Open MEGAsync (link). Enter your login information. MEGAsync will remember it for later use. Wait a minute or two for Mega to complete your login to their cloud. They use key encryption for security, and that’s a good thing! You’ll see an ‘M’ icon at the top right of your screen in the menu bar. Click, and a window will open.
Click on ‘Syncs’ at the bottom left corner and choose ‘Add Sync’. (Another way to add syncs, and to enable or disable syncs you’ve already added, is to click on the Settings icon at the top right corner. Choose ‘Preferences’, then ‘Syncs’.) Begin your sync, then quit MEGAsync *without pausing* your upload. If you pause it, it won’t automatically start for your automated upload.
SIDE NOTE: It’s a good idea to save a local backup of your Mega encryption key. It’ll make life much easier if you lose your password. Select ‘Account’ in the Preferences window, then click ‘Export Key’.
Next, you’ll make sure you don’t lose your connection while the upload is happening.