How to change the permissions of the site's root directory to 0755 or higher on Open Server?

Question

open server

I install a backup copy of the site on a local server using the Akeeba Kickstart utility.
During installation, I can not select an archive with a backup.
Here's what the Akeeba Kickstart documentation says about it:

Akeeba Kickstart launches, but my archive files don't show up

This usually means that your site's root directory permissions don't allow listing files. Change the permissions of your site's root directory to 0755 or higher. If you don't know how to do this, ask your host; we don't know how each host works. You can also ask your host to grant read and file list permissions to your root website. They will either do it for you or tell you exactly how to do it.

On some hosts we have seen that it is necessary (in addition to the above) to give 0755 access rights to the backup archive and all parts of it if they exist, e.g. file.jpa, file.j01, file.j02, etc. I know. this doesn't make any sense (permissions 0644 on the file should work!), but it looks like some hosts are misconfigured. So, try setting your website root permissions to 0755 and your backup archive permissions to 0755. Kickstart should be left at 0644 permissions or you risk getting an internal server error 500.