How to setup a field to contain Next Number?

I created a table with UKID as the primary key field and 2 fields, First Name and Last Name.  This field will contain a next number. I have two questions please.

1) What's the process to set up so this field will contain a next number please?

2) When I enter in values for first name and last name, does the UKID field automatically gets populated with the next number or I have to manually insert a value into it?

Thanks

JDE 9.1