How restore a Snapshot from Google Drive

Hi. I had what appears to have been a bad plugin update recently that crashed my single site with the current theme and could not get into the admin. I went into CPANEL and installed another theme and can get into admin now. I want to restore a snapshot about 4 days old. (I should also note I just now updated to the brand new core version of WordPress that would be different than the I want to restore. Not sure if this matters.) I downloaded the zip file backup from Google Drive to my computer. What now? Do I have to use FTP in some way? Is there an easier way to restore? Are there detailed instructions already documented somewhere about Snapshot restore? I’ve never restored a WordPress site before. Many thanks.