It's a fairly squat plant by nature, and branches fairly heavily. All you really need it to plant the stems fairly close together and let it grow in.
Like all carpets, you'll want decent light and CO2 to see good, healthy growth. To my knowledge, S. Repens is a bit more low light tolerant than some carpeting species, but will still need good conditions to grow into a carpet. Tom Barr's tanks run fat on the CO2 and ferts but with medium-medium high light, plus
aquasoil and other amenities, which lends to his success with it.