How much weight to lift depends on your fitness level. Are you new to exercise or have you been exercising a long time or have a sport you play. Bike riding and swimming are not wright bearing. You need to stress the bones. Weight bearing exercises anyone can start with are climbing stairs, dancing, skipping, hopping, jumping jacks.
If you jog, that’s wright bearing as it puts stress on the bones. Tennis is another sport good due to the stops and starts and sometimes sprinting that is needed.
I use 2lb. ankle weights when I exercise as it adds more load to my exercises. I also hold a 10 lb. weight when I do squats as it increases the load.
Google exercises for osteoporosis and you’ll find some good examples. Dr. Fish man has yoga poses good for osteoporosis. Also check out Margaret Mead who tackles this subject as well.