Float tag problems

First, I want to say wordpress and this community are awesome. I hope you guys can help. I have a rather simple question, as I am new to css, etc. the problem can be found at https://www.pierce-reagan.com/journal

i’m trying to line up my main body text with my header image, which is centered based on text-align: center; tag. right now there is a space between my body and my sidebar, which looks like the aread of float: center that I want filled up with the body text (including the brown background) instead of a blank space with the black background. i also want to make sure these proportions and spacing remains contact when resizing windows.

can you guys help? thanks!