I purchased ether during the presale. Is there an easy way to import those ether and start using them?
Using Mist (Update 27th of February 2016)
It is now possible to import your pre-sale wallet in the official Mist wallet, version 0.4.0 and up. No more command line interface required.
To import your presale via Mist / Ethereum Wallet, start it up, let it sync (takes a day or so), go to "Accounts" -> "Import Pre-Sale Accounts". That's it.
In some versions ~0.5.0, it would return a "invalid" password even when the password was correct. If that happens to you and you are sure your password is correct, you can import using Geth (below) and it'll automagically show up in Mist.
Using Geth (Original text)
Geth has the ability to import a pre-sale wallet.
You can do this using
geth wallet import path/to/presale.wallet. You can also add a
--password flag with a path to a file containing your password to do it non-interactively.
Once Geth has your wallet you can use the official Ethereum wallet to start interacting with your Ether.
It depends on what you want to do with the ethers held in your presale wallet account.
Just to clarify what keys you have, here is a example of a set of keys:
Unencrypted private key:
Private key encrypted with the password
You should have your encrypted private key, and password to decrypt your encrypted private key and your public key.
If you just want to verify that you have access to use your presale wallet ethers, you can enter your encrypted private key with the password into MyEtherWallet or the EthAddress.org wallet . If the public key generated by these wallets match your presale public key, you have the necessary information to spend your ethers at a later date. You can check that your ether amount is correct by entering your public key on the blockchain explorers https://etherchain.org/ or https://etherscan.io/ .
When you want to spend some or all of your ethers, use the Ethereum Mist wallet or MyEtherWallet. The Ethereum Mist wallet only allows you to import your unencrypted private key, while MyEtherWallet will import both unencrypted and encrypted private keys. Once loaded, you can send your ethers to a destination address.
Ethereum Mist Wallet
The Ethereum Mist Wallet runs with a full Ethereum node in the background that will take up 13 Gb (currently) of disk space for the blockchain data and may take several days to synchronise the blockchain with the Ethereum network. This wallet will allow you to import the JSON presale wallet in the front-end GUI. You will have to the use backend "geth" Ethereum node software to import your unencrypted private key. You can download this software from https://github.com/ethereum/mist/releases .
See Is there a way to manually import a private key into Mist? on how to import your private key using the "geth" program to import your unencrypted private key into the wallet.
Once your private key is imported into geth, your account will appear in the Ethereum Wallet application and you can spend your ethers.
There is an Send Transaction tab where you can paste your encrypted private key. The web page will then prompt you to enter your password. Then click on the Decrypt button. You don't have to send any transactions if you want to just verify your private key.
You can use the wallet at https://ryepdx.github.io/ethaddress.org/ to convert your encrypted key + password into an unencrypted key. As with MyEtherWallet, you can run this wallet directly from the website, or you can download the source code from https://github.com/ryepdx/ethaddress.org onto a computer not connected to the Internet and run the wallet software if you are concerned about security.
Click on the Import Wallet option on the left of the screen. You can then paste your encrypted private key and click Unlock. You will find your unencrypted private key on the bottom of the image, displayed upside-down.
You can now use this unencrypted private key to import into the Ethereum Mist wallet.
The easy way
The safe way
If you don't want to give an exchange access to your funds, you should download the command line client, geth, and use the command
geth wallet import /path/to/my/presale.wallet
See the Ethereum Gitbook for more details
I like using this tool - make sure you're on the right site and there's a green lock on the address bar - learn some coding if you want to use the safe way:
It's pretty easy to import your wallet.
Unfortunately, it appears you didn't follow instructions by keeping the json wallet file. If you only have the password, your ether is lost, as clearly stated in ether sale documentation, instructions, and FAQ:
KEEP YOUR WALLET AND PASSWORD safe. Without your wallet AND password, your ether will be unrecoverable, permanently.
If you didn't receive the wallet when you made the purchase, the same FAQ says: "Contact firstname.lastname@example.org immediately."