I also have one and have used it a bunch this summer! Basically, you pull the cassette out and open the screw cap. The cap should double as a measuring cup. I then pour some of the blue sanitizer liquid in the cup and dump it into the cassette holding tank. Then place a little water in the tank...enough to cover the bottom. Screw the cap back on and then place the cassette back into it's holding area.
Next you will need to fill the flush tank. There should be a little pipe that pulls out which also has a green cap on it. Pull it out and start filling it up...this is the water that will be used to flush the toilet. There should be a little clear tube which will show you how much water is in the tank...mine starts to fill really fast when it is empty, but when you get towards the top, the tank gets bigger and it takes a while to fill. I fill mine until the water in the tube is at the very top. When full, put the cap on that pipe and and fold it back into the cassette area.
You should be now ready to do you business! We only use our for going #1...mainly middle of the night type stuff, but one of my daughters did have an upset stomach one time and had to do a #2 emergency once and it was fine for that.
To use the toilet, there should be a little lever that opens up the hole in the bowl...you can either go and then open the lever or open it up and go...either way, you open the lever and then push the flush button. Ours usually lasts about 2 days for my family of 4 before I have to empty and refill it....when the flush tank gets empty, you will have an indicator light come on and it will run dry. One time, we did fill up the waste holding tank before the flush was empty and I had a little bit of a mess inside the cassette area to clean up, but you will see if it is getting too full.
Once it is full, just make sure the lever is closed for the bowl flush hole and then go outside and pull the cassette out. You can then take it to the dump station or a bathroom...I actually prefer to take it to the bathroom and it is easier to dump without making a mess. To dump, you fold out the pipe with the measuring cap and then open the cap...then just hold onto the handles and tip it up to dump and push the little green button to release the air and it will dump out. I usually put a little water in and rinse it out a couple of times to get all the TP out... It is then ready to go again! Good luck with it!