Your Website Backup Is Working, but Can You Restore?
In a previous post Do Your Own Website Backup, I explained why you should do your own website backup, even if your web host does regular server-side backups. I covered how to do your own backups using the All-in-One WP Migration plugin.
But any backup plug-in is only as good as its Restore function.
And you don't want a real-time emergency be the first time you check it out.
So let's go through using All-in-One WP migration to restore a website from a backup file it previously created. We'll use it in a real life situation to transfer a website from one host to another, backing up the site on the source host and restoring it to a new, empty site on the destination host.
The Backup Files
Backup Files created by All-in-One WP Migration have the extension .wpress with the first part of the file name containing the domain name.
I create one after I make any change to my website that I'd hate to lose. I download the backup file to my local hard disk in a folder associated with my website and keep three generations.
Restore Example
I have a new website that I've created on another web host, done a backup and will restore it to a new, empty site on Wealthy Affiliate.
Important: Make sure you have a record of this site's username and password. You will need them to get into the new site after the restore has been done.
Step 1: Point the Domain to WA's servers

DNS propagation takes some time, so we may as well do it first.
The domain name is hosted at Namecheap, so we go into the Manage Domain section and change the nameservers to point to Wealthy Affiliate. Propagation starts as soon as we click Save but can take 24 hours or more.
Step 2: Create a New, Empty WordPress Site at the New Host
This is something we've all done, but here are the steps.

a) Build a website on a domain I own.

b) Enter the domain name and title. Select any theme. It doesn't matter which, as the theme will be replaced by the original website's theme when we restore it. This is the nature of the restore. Everything is restored, including the theme, the pages, the posts, the menus and the plugins.

c) Wealthy Affiliate builds your new, empty WordPress website.
d) Now go to your new site's Admin Details and click on the Login Now button. Note that you may have to wait until domain name propagation is complete before you can log in. If propagation is not complete, you will get a 404 Page Not Found message.
Step 3: Add the All-in-One WP Migration Plugin

The only plugin you need on the new site is All-in-One WP Migration.
Other plugins may have been added by your web host's installer. That doesn't matter, as the restore will replace all the plugins with the ones that are installed on the website you are transferring.
Of course, you can change that after the restore if you wish. After the restore has completed, you can do whatever you want with the website, as if it had been built on the new web host.
Step 4: Import from Backup
From the left-hand menu, select All-in-One WP Migration >> Import. Then click on File.

Select the backup file previously created.

You can select the file by double-clicking on it or by highlighting it with a single click and then clicking on the Open button.
As soon as you do so, the restore will start and will show a progress message. Now it's time to sit back and wait. Have patience.

Important Note: A restore takes much, much longer than a backup.
When the import has finished, click the Proceed button to complete the process.

The warning about ensuring that you have a backup has always struck me as strange, since it's a backup you're restoring from! I guess they're just making sure they have all their bases covered.
Important: Don't forget that once the restore is completed, your admin username and password will be the ones associated with the original site, not the new ones assigned when you built the new empty site.
Again, be patient, there's lots of complex stuff happening behind the scenes. After you click the Proceed button, there will be a pause then some progress messages as your new (old) website is being updated.

The final message you will see invites you to click on the Finish button.

You can ignore the other two optional invitations. Click on the Finish button and you're done.