I am a Junior JS Dev, new to Ethereum. I am trying to test this Dapp ( Ballot ) locally, have all the pre-reqs ready, but not sure how to open it from the mist browser.
Will appreciate any help.
In summary, navigate to Contracts -> Deploy New Contract, then paste the contract into the source code textbox and the send/submit. The wallet will send the compiled bytecode to the network.
You will need a little Ether to pay for the gas needed. On testnet, this is easily acquired through mining, at no cost. After the contract is deployed, you'll see it tracked on the contracts panel.
Alternatively, consider experimentation with the in-memory Remix (a.k.a. Browser Solidity) browser solution. https://ethereum.github.io/browser-solidity/
This is an in-memory solution that doesn't persist between sessions. It's fast and there are few prerequisites.
Hope it helps.