Hi Rholou,
If you have electric service at the RV park, leave the power connected to the pedestal and the power converter will intelligently manage the battery to keep it fully charged.
If you don't have power, the next best choice would be to have a generator that you can use for backup power and to charge the battery.
A third choice would be to remove the battery, take it home, and keep it charged at home.
A fourth choice, although not as effective, would be to connect to your truck and use the truck to build up a charge on the trailer battery.
If you really get stuck, there's a manual procedure in the manual that illustrates using a battery powered drill with a hex bit to manually operate the hydraulic pump. You also need an allen wrench to open and close the appropriate control valve.
Whether you need to open the slide or not, you don't want to let your battery run down. It'll shorten its life.