We recently made the decision to transform our dining room into a playroom for the kids. Our dining room was open on two sides with arches as entrances. I completely closed one in and framed the other into a squared off doorway so I could install doors later.
I used studs from the lumber yard to frame the new wall sections. I rented a concrete hammer to secure the new wall sections into the slab to make the new wall sturdy. I also extended electrical outlets into the wall section. (under the supervision of an electrician)
After finishing the framing, I hung sheetrock on the new walls and painted textured and painted them to match the rest of the walls in the house.