Configuring Forms

To configure a form, drag and drop such fields as text columns and drop-down lists onto the form and lay them out. Up to 500 fields can be placed in a form.
Creating an App from Scratch page also describes details on how to set forms.

For each field, you can set the field name and whether that field entry is required.
To configure a field, hover the mouse cursor over the setting icon Gear icon on the upper right side of the field, and click Settings.

Select Fields in Accordance with Your Purpose

Purpose Field to be Used
Display numbers unique to each record. Record number
Display descriptions or cautions when data is being entered on the form. Label
Add a blank space to the form. Space
Display a date or time value.
Add an option item to the form where only one option can be selected.
Add an option item to the form where multiple options can be selected.
Add an item consisted of "Yes" or "No" to the form where either one is to be chosen. Check box
Enable data to be retrieved from other apps. Lookup
Show the record list of an app on the form. Related Records
Group fields. Groups
Use fields to create a table. Table