How do I edit .DDLs?

When I attempt to decompile a DDL to change the source code it say's that it is not a .NET assembly. How I do I edit cheats?

To put simply, if its compiled you wont be able to edit it without the source code. (unless you are fluent int reverse engineering)

Just to reinforce what was said above. Judging by the fact that you had to ask a question like this. You can't.

not every dll file is .net assembly
you can use x64dbg to edit native dll (or any other debugger that supports dlls)