On soft ground you may want to put 2 x 10s under the landing gear for more surface area. I use 2x 10s under the wheels to level it is very easy you need a carpenters level (or other level). Just pull the trailer onto the 2xs )
The lego levelers are nice but for me 2x 10s are much cheaper & if you loose them no big deal
You need wheel chocks to keep the trailer from moving or rolling off........
Been discussed just do a search.......about leveling. The trailer needs to be side to side level as well as front to back level.
Covering the wheels in storage is a good idea the sun is your enemy