It's a root plant, so trim the roots a little bit (the tips and cut off any dead roots) to promote new growth, then just plant them in the substrate.
If you want to attempt a carpet, you could spread them out a bit to see if they will fill in, however carpets require high light and CO2. I have micro swords in my 10 gallon tank which is low tech at the moment and I dose liquid fertilizer and have root tabs underneath them and they look nice, but they haven't spread or anything. I do like them a lot though looks-wise, and I'm going to try to get them to carpet for me in the future.