A backup is more useful when you know which parts of the site it contains and how long it takes to restore them.
Pick a recent backup and check that it includes the data your site needs, such as the database, uploads and configuration. Restore it to an isolated test location with access restricted to your team. Keep the live site separate during the exercise.
Open a sample article, confirm that its image loads and test the administrator login. Record missing files, the time the restore took and any steps that required help. Update your recovery instructions while the details are fresh.