second page

Just add more measures (ctrl/cmd B). The pages will automatically be added to fit the measures.

(Also, the handbooks for MU3 and MU4, and maybe MU2 are still available.)
Edit: I cannot find the V2 handbook, but there is a how to section if you use this version and need it. https://musescore.org/en/howto?version=2.x
Feel free to search for what you need on the forums.

Which version do you have? The current version is 4.2.0 and the handbook is here https://musescore.org/en/handbook/4

The previous major version was 3.6.2 and the handbook is here https://musescore.org/en/handbook/4/handbook-musescore-3x

Links to other handbooks for other earlier versions can be found here https://musescore.org/en/handbook/4/appendix

Regarding adding pages, and assuming you are using the latest version - read on.

Once you have filled page 1 Musescore will automatically create a page 2. If you want a page break before then use SHIFT + RETURN to add a page break.
See https://musescore.org/en/handbook/4/pages-and-vertical-spacing

If you want more measures go to Add>Measures and complete the dialogue. See https://musescore.org/en/handbook/4/adding-and-removing-measures

If you are still stuck come back and explain in more detail what you want to do, how you have tried to do that and what happened instead of what you wanted.