arms
I do old school pushups.. LOL. But if you aren't strong enough for that start doing wall push-ups and work your way to the floor. Also invest in some hand weights and do curls and tricep kick backs. Also doing dips on the edge of a chair will work the backs of your arms. You can check out you tube so see all of the things I just described...They can be challenging, but they do help.
A couple ideas. Youtube and see what is out there...Get ideas online. While you are doing the elliptical you can use your arms to push/pull against the arm/hand polls. The other thing I will do (when I do my walk inside the house {like rainy days}) is I will do push ups against the kitchen counter. Just lean into a counter and do modified push ups. Start with 5-10 then build up. I got up to about 31...I do 30 but always do and extra one in case I cheated!! I made sure my chest touched the counter...