Trying to upload a plug in

Hi there I am a complete amateur at WP, and am trying to get my WP site to give me full page photos - not just reduced sizes. I saw that UPFRONT allows one to alter the page to suit, so I asked to trial it, but gather that one first needs to upload the "wpmudev-updates" that I have downloaded - however when I openly WP site I cannot see how to load it. I gather that once loaded I will be able to upload UPFRONT

Please help - my email address is