Instructions are mentioned in watched apk homepage.
Alternate Cloning Method
1)Download the official app from here
2)Do not launch
3)Now download and install Clone App
4)Now click Clone App and clone Watched.
5)Launch Watched from clone app all the time and Watched APK Premium work without fail, or at least for 2 hours.
Source: Shubham from Discord and /whatchedapp subreddit