On the mower itself, you should be able to adjust the support bar out. If the bar is all the way out, you'll have to adjust your left lift arm on the tractor, provided it is adjustable.
Set the right lift arm adjustment about in the middle. Remove the link from the left lift arm. Turn the left link out so that it is longer to the ground. If the left arm link is not telescoping, buy one.
If the left link is slotted, make sure you have the bolt through the bottom slot. A pic of your 3pt hitch and current settings of the mower would help.
Another prospective problem could be the right side weight can be too much for the tire. May need to pump the tire up.
I'm not familiar with the mower, is there an adjustable skid or shoe at either end of the mower?