You wanna download the current version of autohotkey, I'd recommend V2 but I have no idea what the syntax is. After downloading I think it will create a script for you called something like "AutoHotkey.ahk". You can place this anywhere but I put it in my Documents. Once you've found a place for it you will want to copy it. Then go to C:\Users\%UserName%\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
. Finally right click and select "Paste shortcut". This will ensure that AutoHotkey runs on start up.
To make any adjustments, which will be many at the start, find the AHK icon in the notification area. Right click and select "Edit This Script". This will open notepad for you to make changes in. Once you are done save and then right click the AHK icon and select "Reload This Script"