Can't download anything? :c

[Dawnstorm]

At first it was just the items. The Pawsome Pack I downloaded didn't work so I just gave up on it and went without items.

But then I tried to download a bunch of maps and presets. They didn't work either. I did everything the "Read Me" notepads tell me to. Q_Q Is there just something wrong with my files?

[OchreKangaroo]

I'm pretty sure you're probably installing it wrong even though you're looking into the "Read Me". But, the files could be corrupt too.

A tutorial on how to install item packs.

https://www.youtube.com/watch?v=1WmsPQUceKE

For the maps, they could no longer work. But, I don't have too much experience on maps and presets so I'm probably the person you WON'T ask for help about them. x'D Hope some of this helped. Maybe try installing other maps and see if it is your FH or the maps you wanted to install.

[CatCake]

Well, you have to make sure to have WinRAR. If you don't have it, you can always download a free trial. Are you actually sure you've putted the files into the right folder. Try by deleting the files, then downloading the same thing and try again.
Maybe some tutorials will help on YouTube, you've probably got something wrong. If you tried many times correctly, but still nothing, you should probably contact the creator of the map/preset/item(s), maybe they could help?
I've only had trouble with items, but now everything is alright. I'm pretty sure your problem can get fixed too.
Here are some tutorials:
-maps: https://www.youtube.com/watch?v=1ULvvPVJIk0
-presets: https://www.youtube.com/watch?v=dIFjZ-ww0jM
-items: https://www.youtube.com/watch?v=Ew8Mz3mD9ss
-mass markings: https://www.youtube.com/watch?v=b0EpEpcJ_Zw
Now, if you are using Mac, then I'm sorry but I cannot help with that, since I'm only a Windows user. I think there are some differences between Windows and Mac downloads.