If your goal is to have all posts from a certain category appear in a page on your menu, this is how to do it! (This actually doesn’t involve pages at all!)
1. On your dashboard, under Appearance, go to ‘Menus’.
2. On the left side of the Menus page, there should be three boxes labled: Pages, Links, Categories. Click ‘Categories’ to expand the menu.
3. Select which of your categories you want to have appear in your menu as it’s own tab, then click the ‘add to menu’ button.
4. Then, look as your new menu item appears to the right in the ‘Menu Structure’ area. You can re-order your menu items here, and even make a category a sub-tab on your menu by dragging the item slightly to the right underneath the menu item you want it to appear under.
5. Finally, make sure you select ‘Primary Menu’ rather than the box next to ‘Auto add pages’, and then hit ‘Save Menu”. You’re done!
Thanks to our Posiel TA Michael for teaching me how to do this!