You can just buy some CYA and add it outright instead of using dichlor if you want. You may have to buy it from a pool store, but just don't buy anything else while you are there. You might find it at Walmart or someplace. It might be called stabilizer or conditioner but if the ingredients say cyanuric or isocyanuric acid, it is the right stuff. Add enough per package directions to get to about 40 or so. Add it slowly to the skimmer while the pump is running and then do not back wash your filter for at least a week and run the pump 24/7 for four or five days while it is dissolving.

Another option is to just use the dichlor that you have on hand to add the CYA as you chlorinate. Though your chlorine level was 10ppm when you tested, it isn't going to stay there if you currently have no CYA in your water. So, as you need to add more chlorine, your dichlor will gradually be adding CYA. Monitor your CYA level every couple of weeks and when you get to 50ppm, switch to either bleach or liquid chlorine.

A third option is to add some CYA now to get to a reading of about 25 or 30 and then to use dichlor for awhile to get the rest of the way up to about 50.