Window → Workspace → Interactive for PDF
create text for a label
create an object such as a rectangle for the form field (you can also make custom shapes for radio buttons/checkboxes, etc…)
Open the Buttons and Forms palette, on the right side or also under Window → Interactive → Buttons and Forms
with the form field object you created above highlighted, use the Buttons and Forms palette to set the “Type” appropriately, such as a Text Field, then give it a Name and set any other desired options
continue creating the remaining fields on the form
if you want to control the tab order, you can use Object → Interactive → Set Tab Order, or open Window → Articles, drag each form field there, then reorder as desired