[I'm a dumbass - Need help with Mozilla settings]

I know I worded the question in a vague, bad way, but..

 

Yes! That did the trick! Everything is fine now. Thanks so very much.

[I'm a dumbass - Need help with Mozilla settings]

I came back to modding Skyrim yesterday. Or, tried to at least.

 

I started downloading a mod and a pop-up window came up that asked me with what do I want to open the file with. Since I'm half-cocked (yes, that's a word), instead of choosing Nexus Mod Manager, I chose Mozilla Firefox. After that, tabs started opening up mad. Like 2-3 of them each second, all with the file name. I can prevent this by closing my browser entirely, but I can't download and install mods through nmm like this. I tried toying with options in the browser, but since I'm no tech wiz, I can't do it.

 

Helpsies?