I want to make wordpress look like my main site area… customize

Hello, I have little css skill, I designed a nice site but need the wordpress to be able to set up users to post information. I want to be able to make my wordpress pages look just like my main site area so when someone clicks on that page it does not look too much different. If I can change the header, back ground color, that is good enough.

My header on my main site has my website navigation on it, I know how to change images etc, so if I can get the back ground color changed it is a start. Also if I can add my image header with my navigation and make them clickable that is real good. Ronnie Lees.

https://www.northeastsurfing.com/images/general/nes_header.gif

draft of page. https://www.northeastsurfing.com/draft.html

Note: is it hard to make a simple theme, or is it better to make the small changes above.