I only use body weight when strength training. what should i do not using dumbells to increase intensity?

Weight Training : Do less reps with more weight to fatigue your muscles. Start first set with no more than 6 to 8 reps, rest only 10 seconds or less and then go to second set. Object is to fatigue your muscles, last rep should be all you could possibly do. Monitor your progress and increase the weight when certain exercises become much easier. Best wishes.