you can also do hammer curls cross curlling standing up for stabilizing muscles and the you hold the dumbbell the same and curl to you opposite shoulder which you will see big gains in size of arms. I love cross curls to change up from normal hammer curls.which can be done sitting or standing it's harder to cheat when sitting.also inclined bench for dumbbell curls is what I do also for more stretch more movement equals more room for muscle. Hope this helps.

u could do it sitting down just make sure to sit up straight