how to assign one role to one form ?

Sorry it’s me again.

I created one form registration for one role of users but I don’t know how to assign each role to each form.

I found this :
“Assigning a role to a form is easy and you can select a role by going to the customize this form widget situated on the right-hand side of the page. In this widget you can assign a role to this form. If you have not yet created a custom role then select roles from the Ultimate Member sub-menu tocreate a new user role. If you do not asign a role to this form, any users signing up using this form will automatically be assigned the default user role (member).”

but I can’t see any widget on the right-hand side of the page

thank You.