When creating a new menu, I am not able to link a new menu entry to a collection.

Hello! I am new to Shopify and am updating my theme to a paid theme and am using a trial to theme to see if I like it. I am trying to create a new mega menu (the trial theme supports this) but as I am trying to create this new menu I have run into a problem. When I create a new menu item, I am not able to link a collection to it. I am able to link anything else to it (“all products,” my home page, blog pages, etc). The collections link up just fine to my images in the the new theme, so I don’t know what is going on. Any help would be appreciated! thanks in advance!

Never mind…I figured it out. It turns out that the apply button could not be seen or scrolled down to, but when I made my screen full sized I was able to the see the “apply” button.