How to lookup Customer name from user email

I have column name as User email and I already put Useremail() as initial value so the value reflect in current Email user but for next step that i want to do is shown customer name autometic by link form user email

For example I have table as below
Customer Email : AA@gmail.com, Cutomer name : A
Customer Email : BB@gmail.com, Cutomer name : B

When email AA@gmail.com is sign in
The column Customer email will shown form formular Useremail() as AA@gmail.com,
**the column Customer name must show : A **
What the formular that I should set up to make customer name show up.

You can read it for example like LOOKUP(USEREMAIL(),UsersTable,Email,Customer Name)

Thank you for valuable advice.