Creating my multisite

Hi, I am not by any means a WP advanced type of guy so I need some help here. I am working on a project where the customer wanted to achieve two different things so I choose to create a site with a theme and plugin I liked and then created a subdirectory for the second area of her site to achieve the other.

My question is what should I do on this? I am a bit lost on creating a multi site as I’ve never done before. I have two separate themes working however I want clients to be able to login to one and not have to login again when going to the subsite. Any advice would be greatly appreciated.

Thanks,
James

Site:

http://www.silver-services.net/

http://www.silver-services.net/jobs/

Again to be as clear as I can… the only thing I want to achieve is when someone logs ins or registers to post on the initial site… if they go to the subsite, I don’t want them to have to login all over again.

Thanks!

James