The only way to register on Butter is through getting an invite from your employer.
The invite will come as an email (remember to check your spam / junk folder), which looks like this:
Press the 'accept invite' link and you will be taken to the following site:
Once you've confirmed your first name, last name, email and password you're good to go!
As soon as you register your shift data is imported into the app, so you can get full value from Butter as soon as you download the app 🙌