If you want to play on the server, download the jar in this link:
[Only admins are allowed to see this link]If you don't know what to do with this, here's a step by step:
1. In your computer's search menu (shown below), type %appdata% and hit enter
[Only admins are allowed to see this link]2. Click the .minecraft folder
3. Click the bin folder
4. Find the already existing minecraft.jar, and replace it with this new one.
5. Now DO NOT update your jar when you boot up minecraft
6. Done