WORDPRESS EXPERT- NEED CHILD THEME FOR OPTIMIZE PRESS

I had a really bad experience and paid fast but was not satisfied, so please on this project I need you to read carefully my requests. Communications needs to be good I need an optimize press child theme... so that i could modify myself in the future.... I need to add sidebar support to all my posts.....last freelancer did this but did not make child theme so i don't know what he edited.....he did not want to tell me I need the footer to appear in all my posts to.....I know a little about wordpress but do need somebody that can explain just a little on what css codes i can use on my child theme to call commands like to put (sidedbars on all posts) to put (footer links on all post) etc. So if you don't mind fixing this little things and explaining a little css this is the job for you... thanks