Change margins in powerpoint

I am in desperate need of some help. I am trying to print out an 11x17 color
powerpoint slide. The margins are not working for me. There is either too
much space on the top and bottom or too much space on the sides of the paper
when printed out. Does anyone know what my margins should be set up as?
Should I put the page setup as 11 x 17 or should I make a custom slide. I am
so frustrated right now I am about to pull my hair out. Please help!