Ok, so you have your file,say Tune Up 2008:

I suppose you have
Win Rar installed.
So,
Right click on it and select
Add to archiveBox like these appears:

Here you can change the name of archive,but be sure to leave .rar extension at the end.
If youre file is bigger then 100 mb and you want to split it to upload to RS simply add
100m in box,like here:

Now lets create the password.
click on
advanced tab,you get this:

Click on
set password, and box like this pops up:

Finally enter your password (like stealth_science) and confirm it.
Click OK, box closes, and then click OK on main window.
You are done!