If you originally created a Clipchamp account using Microsoft, Google, Facebook, Dropbox or a magic link, and would like to add an email + password login option instead, it's simple, as long as it's for the same associated email address (e.g. the same email address you use with Microsoft, Google, Facebook, Dropbox or the magic link).
All you have to do is:
log out of your account
click sign in / sign up
go through the steps to sign up with an email and password shown in this article
Because Clipchamp automatically recognises different login options that are connected to the same email address, the system will be able to associate and combine them with the same Clipchamp account. So in future you will be able to login using the email and password you created, or indeed any of the other log in methods available.