Click on the Form tab and then click on New.

Identify the primary object to be used for this form.  

The system will add the object identifier field to the form.

Click on the Items tab in the form builder.

Drag and drop all the fields you want to have on the form.

Click on each field and set their properties.

Add conditional rules if needed to dynamically determine (as the user enters data) which fields show and which fields are hidden.

Add related lists.

Add additional components.

Click Run to see what the form looks like.

Save the form.

Optionally attach the form to a step in the process builder.

Or make the form available to your users by…