You can utilize WordPress’ category feature. Just add a Category for your posts – either “how to” or “affiliate marketing”, and then in Appearance > Menus, open your primary nav menu and add the two categories as a menu item.
What I’m understanding right now is you want to separate “how to” and “affiliate marketing” in different pages.
By default, if you set a category for your post, there’s going to be an archive generated for these categories. Thus, you’ll have a separate page for the two, that is, the “how to” category archive page and the “affiliate marketing” category archive page.
If you’re referring to something else, let us know.