Open Source Website

I am looking at CMS and open source websites so that I will be able to edit the content.  Now I just have to figure out how to actually put the thing together.  I have the banners all separated.  I thought I would download it and I would just have to edit the text, which apparently is not correct.  It is hard to weigh the opportunities that the site will actually provide, but a site that I can change is definitely the right choice.