I am sure everyone would like to help you, but we need more information. What type of turfgrass do you have now? Would you like a high or low maintance lawn. Do you have much shade? Are we going to work with what you have now or is resodding an option. Pictures are also helpful.

Yes pictures are very helpful. In this case I'm not sure any of joneboy's other questions pertain. Why? Creeping Charlie. Until you get rid of that, you can't have a lawn. Killing the CC will require repeated applications of Round Up to get rid of. If there are any living roots left after a couple weeks of Round Up, the CC will return.

I would wait until April to start killing it. By April all the weeds you're going to have should be growing. Supposing you sprayed the first RU on April 1st. Then water it every day for about 20 minutes trying to get new weeds to sprout. After a week, spray the RU again. Rake up all the dead grass and weeds and install the new sod. St Augustine only comes as sod. Be sure you are ready to install it the day it is delivered. The longer it sits on the pallet the better chance you have of fungal disease.

You do not have to spray round up to get rid of creeping charlie. Creeping Charlie can be selectively removed from cool season turf with a 2,4D and triclopyr broad leaf herbicide and from most warm season turfs with 2,4D,MCPP, and dicamba. Also, growing a healthy vigorous stand of turfgrass will help.