I cannot deploy a contract using Mist because of the error intrinsic gas too low
How can I increase the value of it?
You can type the gas you want in the blue underlined bit. Just click on it and type
While deploying the contract, you can specify the amount of gas you want to send with the transaction. On the bottom left of the page where your write your code, you can see a slider bar for Select Fee
, Just use the slider to increase/ decrease the gas you want to send.