as it says in title how do i download skins do i need to put extra money on s2 license?

For Hi res skins, yes (2 pounds for 2000 skins I think).

As for normal skins, you download them when you join the server.
You need to enable Automatic skins download somewhere in options.

Edit: You can also download skins when you watch a replay.

You put them in your skins folder in your LFS directory.