when i try to add it it says access denied

Could you provide more details as to where you are seeing "access denied"? If you mean via FTP, then you'd need to contact your host as they aren't allowing you to upload DLLs.

I can't upload the file it says I don't have enough permission, I am using gameservers.com to host my RUST server and I'm using FileZilla to transfer files.

You'll have to contact your host.

i was at gameserver before.

Wulf is right, you need to contact them, and ask them to add it .
they will do it manually..
so for each update, you need to ask them again.... (lol)
they told me they will add it to the mod installation section, but after months without it, i just left :D