I think there's an article on cleaning the filter in Pool School, and there are a lot of YouTube videos as well, but the process is pretty straight forward.
1. Turn off the pump
2. Separate the bottom and top halves of the filter case
3. Remove the filter cartridge and spray off all of the debris until it is clean and white (or replace it, if it is in bad shape - broken bands, torn filter material, etc.)
4. Place the cartridge back in the housing and secure the halves together again
5. Turn the pump back on and note the new filter pressure on the gauge.
When the filter pressure increases, perhaps 10-15% or so, that is your indication the filter needs to be cleaned again. For most pools, this is probably around two or three times per year.
I'm surprised nobody has mentioned this yet, and it is thoroughly covered in the Pool School articles, but pool care starts with knowing the condition of the water. You will need a good water test kit, and everyone here recommends using Taylor reagents as they're high quality and readily available. The Taylor K-2006 kit is excellent, and the same reagents are also repackaged and used in the TF-100 kit from TFTestKits. There is also a very good mobile app called Pool Math that you can enter the test results into and it will tell you what you need to make sure the water is clean and healthy for your pool. With these tools maintaining your pool is not only easy, it's also a lot less expensive than paying someone to do it for you.