As of now I only have one 15 pound dumbbell, what exercises or techniques can I use to get the most out of it? If there are any other good ways to strengthen arms or biceps without the use of equipment, that would be appreciated as well.

I am a guy and aged 16. I have just bought a pair of dumbbell and wish to tone up my arms and upper body. My arms and chest are saggy, so i wish to use a dumbbell to tone them up. How many times should i do in a week to see improvement and what are the ways to use the dumbbell correctly. My aim is to tone up my arms and chest in a month, can that be possible?