First of all you will need to create an account on the store, or log into your existing account if you have one.
NOTE : This is NOT the same as your standard Focusrite/Novation account.
https://store.focusrite.com/en-gb/login
Once logged in, create your wishlist by clicking the heart icon next to any products you would like to add.
Items added to your wishlist are automatically saved if you are logged into your store account.