You can create a file-type information field by going to Users & Companies / Information Fields and clicking Create New Information Field.
When Field Type: File is selected, you must choose your service provider (Google Drive or Dropbox) and connect it to your account.
Usage Areas:
Forms: Allows people filling out membership registration forms or other custom forms to upload the requested documents.
User / Organization Profile: Users or organizations can upload documents or files directly to the relevant information fields on their profile page.