Hi there!
Shopify has changed the location of your domain setting
To access it:
Click Settings
Click Domains
If you need to add your domain you purchased, click connect existing domain
If you just connected your new domain, it will probably say SSL Pending, that's okay!
You will also see your Shopify Domain below which will have a - and myshopify in it. This is like a backup domain, your customers won't see that.
Screenshots of steps are below:
