If you downloaded the file and didn't choose a specific folder, you probably downloaded it to /home/user/MyDocs/

This page explains how to get root. You will need it to copy the file.

So:

1. Download the file. You need to know where you downloaded it!
2. Open a terminal.
3. Get root.
4. Go to the directory where you saved the file. Assuming you just saved it to the default folder, you type:
   
   Code:

   cd /home/user/MyDocs/.documents

   (thanks Brontide!)
   
5. Unzip the file. Type:
   
   Code:

   gunzip liboscar.so.0.0.0.gz

   You can cheat and hit the Tab key after typing "libo" and it will fill in the rest. If it doesn't you're probably not in the right directory.
   
6. Copy the file to the correct directory. Type:
   
   Code:

   cp liboscar.so.0.0.0 /usr/lib/purple-2/

   Again, if you hit Tab after typing a few letters and it completes the file name, you're doing it right.