Hi Theresa. Mepis is, I believe, debian based. It should come with a tool called Synaptic - read
this to understand how to use it.
http://www.mepisguides.com/ is a site with guides on using Mepis.
This will all seem like a massive hassle at first - having to read up in the OS to get it working - but it will be very rewarding in the end. And LQ is always here if you get stuck.