The builder doesn’t have a true sign in process. Clicking the button will most likely “log you in” with your glide account, or whichever user you last previewed as. If you want to test as different users, you need to use the “Preview As” function in the builder. You can choose existing users, or you can manually add a new user to your user profile table and preview as them.
If you are looking for a specific page, then you will have to select the tabs at the upper left of the builder, or find a way to navigate to the screen you need.