The Complete button can be found in the inspection's Overview page.
When you are ready to complete an inspection, tap on the inspection row in the Inspections list to present the Inspection Overview page. Tap on the ‘Complete’ button:
A dialog is displayed asking you to confirm the completion:
Tap Complete to confirm or tap No to cancel.
If you tap Complete, you will be returned to the Inspections page. The inspection will be removed from 'in progress' or 'new' status and moved to completed status. It will no longer be displayed in your Inspections List.