How do I arrange the icons manually in the app menu?
Well, As @ Izzy said, it is the app drawer. That's the place where all your installed app icons shown.



So, about your problem, there are two ways you can solve it. You can either go to a third party app like Izzy said or customize your stock app drawer (which comes originally with your phone.

GO Launcher EX, AppDrawer (MIUI App Drawer) and Color App Drawer PRO are good apps.

On the other hand you can find the sort icon in your app drawer (the green arrow) and select Own order. With that, you can arrange your app icons as you wish. You are allowed any number of drawer shelves (pages in the app drawer).