How to create login page?

Answer 1

Well just make a form for text inputs for password and username (and a submit button.) if you want to make it work use MySQL to store the usernames and password and php to interact with. There are many good tutorials online.

Answer 2

filtering and validation of each input is essential.
only store hashed passwords with individual salts.
There is a nice set of video tutorials on youtube by Adam Khoury about creating a social media: you'll find there most of what you need regarding the inner workings of a log in system
https://m.youtube.com/playlist?list=PLlkGN-8wjPHV41Y12LFD8uttbAd1d_ohe