Step 1 to Upgrade to 7.7.2: Wait 2 to 3 years for DNN 4.8, 5.1, 5.2, 5.3, 5.*, 6.0, 6.1, 6.2, 6.*, 7.0, 7.1, 7.2, 7.3-------> 7.7.2 to be released

Step 1 to Upgrade to DNN 4.6.2 Upgrade the site as you would any other upgrade.

Backup backup backup

Extract the files from the Install ZIP

Modify the web.config (connection strings, machine keys)

Paste the 4.6.2 files over the 4.5.5 files

Hit the website

Hope you backed everything up when you realize you forgot to copy the machinekey section of the web.config and can no longer login.