Starting with pushups.

Don't forget to stretch your muscles afterwards. But not to much.
I am short and skinny, 167 cm and was 50 kg when I started working out. Now I am 55 kg and aiming for 57 at christmas.
You should buy these rubberbands with handles. Put the band around something steady, like a leg of a heavy furiture, sit on you knees with your back turned to the furniture and with the bands on each side of your upper arms, holding the handles as if you where making a pushup in the air. start with 10. Turn around and still sit on your knee, keep the band just about stretched, and pull as if rowing. You can also stand on the middle of it and use the handles as "weights" like weight handlebars.
This works for me. Do this "program" two or three times and stretch some. Eat couple of scrambled egg and you will see some results in 14 days.

 

my limit is 10 too