I know that fibronectin can increase transfection efficiency, but I haven't heard of (or conducted) transfection of recombinant fibronectin into competent cells. That being said, you can probably use standard plasmid transfection kits for HeLa (https://altogen.com/product/hela-transfection-reagent-cervix-adenocarcinoma-cells/) and HEK293 (https://altogen.com/product/hek-293-transfection-reagent-epithelial-kidney-cells/), and your transfection should result in fibronectin expression.