How to install it?

I have a problem here, someone please halp.
What do i do with the .rar file i download? usually i do not have these problems,, someone please help!

Unzip it to your mount&blade/modules folder.

you need a programe like winRaR

It bothers me that almost every mod is winRaR. My winRaR trial has finished and i don't know what to do next.
Help?

actually there is a permanent "trial" download out.  You'll have to look for it.  But once you have downloaded the WinWar its not bad at all.  All you have to do is go to Computer>ProgramFiles(usually)>then your M&B Directory>mods folder.  Open up the Mods folder and just open up the winwar with your mods folder still up on screen and move it to the mods folder.  Piece of cake.

get 7zip, it does .rar .zip and .7z files.