Adjusting Photo Size???

Im New To The Photo Uploading Process So Can Any1 Tell Me How To Shrink A Pictures Size After Taking The Screen Shot! I Would Really Appreciate It! :)
Flight Simulator and other chat
https://forums.simviation.com/phpBB3/
https://forums.simviation.com/phpBB3/viewtopic.php?f=43&t=153652
Im New To The Photo Uploading Process So Can Any1 Tell Me How To Shrink A Pictures Size After Taking The Screen Shot! I Would Really Appreciate It! :)