Ok hey guys
i dunno if this is in the right place. or if anyone else has posted it but...

i need to know how to put new interfaces on.... do you need to be registerd or something please help

There are 2 types of interfaces:

Those that require you to have registered
And those that don't

For the ones that do, you simply need to download the interface, and put it's main folder into the Custom Interfaces folder, inside your Soldat directory.
Then you need to select it from the in-game options menu.

For the one's that don't, you need to download the interface, and then put all of the files into their respective places (mostly in the Interface folder). It will then ask you if you want to overwrite the old files (which u may wish to back-up first), say yes and you're pretty much done.
This replaces Soldat's default interface.

Is There a Way to tell if its for registerd or non registerd ppl??

There are a couple of ways to check.

The main way:

If there is a little file included with the interface called "setup.sif", then you need to be registered to use it.
If this file does not exist, then chances are it's fine :)