When done send it the first time you will get a pup-up at the top right saying what it says in the picture.
After sending the command for the second time you wil get another pop-up on the top right with you code in it.
(I have hidden mine on the picture)
When you got you're code click on your profile on the top right and click on settings.
then there is a box where you can enter the connect code to connect you in-game account to the website. 
Also after that make sure to link you're discord account, it will also tell you this when you are trying to get something from the kits page/shop.