More detailed instructions are at mw:Manual:Pywikibot/PAWS and https://github.com/wikimedia/pywikibot/blob/master/scripts/patrol.py

• First create a whitelist of users in your account (or whatever the account you'll be using to patrol) subpage. See wikisource:en:User:Wikisource-bot/patrol_whitelist as an example.
• Go to https://tools.wmflabs.org/paws
• Authorize via Oauth
• Start your server
• Upload or create user-config.py in your home directory. And put

mylang = 'commons'
family = 'commons'

to patrol on Commons. (you must have the patrol right to mark edits as patrolled)

• Click new and then select "Terminal" from the drop-down
• In the terminal text box, enter pwb.py login
• It should give the following response

Logging in to wikipedia:test as <username>
Logged in on wikipedia:test as <username>.

• And then after a successful log in, enter pwb.py patrol.py to initialize the code.