Does it have jacks mounted underneath? If so, you'd use those to level it. I'm not really familiar with the systems, but the general idea is that you have a control inside you can raise and lower each corner with.
If not, you need to raise the "low" tires to get it level. As a former motorhome (without jacks) owner I can tell you that being off level in one direction (side-to-side or front-to-back) isn't too bad, but when it's off in both directions it can get annoying quickly.
For that purpose, I used (and in fact still use with the trailer) the plastic blocks that look like giant Legos. I had 14 and occasionally needed all of them. You build up a little ramp and trial and error to get it level.
Also keep in mind it doesn't have to be perfect. Further, my motorhome, if it was a bit off when I was done with the blocks, would find its way to level after a few hours...but that may have been due to the old shocks.
1995 Airstream Classic 30' Excella 1000
2014 Ram 2500 Crew Cab with Cummins 6.7L Diesel
Sold but not forgotten: 1991 Airstream B190
Sold: 2006 F-250 6.0L Powerstroke Supercab