Download the FTB Launcher from here.
We will begin by making an account. Select the drop down menu to the left of the launch button and select create profile.
Enter your minecraft details into this window. Do not worry, the FTB servers are secure and will not steal your information.
Next, we will choose the installation directory. Make sure that this is in a safe place so it will not get deleted. Also make sure that it is in it's own folder.
We will also choose the amount of ram that will be allocated towards the game. A fair rule of thumb is to not use more than half of your ram. I prefer to use 6 GBs of ram, but you can use as little as 2.
Navigate back to the modpacks tab and select FTB Infinity Evolved 1.7
Select the drop down menu to the left of pack codes to choose the version of the pack.
Select version 2.3.5