Your question is adding solar but it would help to know what make, model and year or RV. I would suggest you do some research and watch some youtubes on solar and installation.
Start with how much solar, ie how many watts do you need to keep your batteries charged. Then do you need more battery capacity or change to Lithium.
I went with a Renogy kit and a few extra items. If you have a "solar ready" RV it probably means there is a port on the roof and medium grade wire run somewhere that is hopefully marked.
Another idea is to go to the Renogy website and watch some of their videos.
I went with Renogy as I liked the quality but there are other name brands and many no names that may be ok or good quality.
I put in 200 watts of solar but wired and bought a solar controler (MPPT type) that will allow for up to 400 watts if I want to add in the future. I also have a 100 amp lithium with bluetooth that is WAYYY better than my old wet cell lead battery.
Ask more questions as you learn more, many will jump in to help.
2017 SLX 195RB
2021 Jeep Grand Cherokee Summit L 5.7L V8
Andersen WDH hitch, Renogy 100 AH Lithium &
200 Watts solar panels from Renogy
Prev. '14 Jeep Grand Cherokee Overland, gas 3.6 V6