A charged batt and jumper cables, u should b good
You wrote that all you wish to do for now is start the engine.
Based on a known good start battery:
Locate your starter. Trace the heavy (battery) wire from the starter to your battery location. Connect that wire to the + terminal of your good battery. Always connect the + first and disconnect the - first.
Now from the battery box locate your - (ground) wire. It will go from the battery to the frame or the engine. Generally the battery clamp for the ground has a smaller diameter than the positive.
Connect this to the - terminal on the battery. Ensure that the frame/engine connection is clean and tight. Poor ground is generally the cause of electrical issues.
Start your engine, and best of luck.
Seth, hire somebody.
Yeesh. It's all about getting to the source. If you can trace that heavy gauge positive to the starter, you can also find the ground close by. Most motorhomes have what's called a chassis battery to run the engine and coach battery (or battery bank) somewhere else that get charged up and runs the stuff in the RV.