Adam,
If you have a GeoXH then you want to choose the Automatic H-star Carrier and Code Processing in order to achieve subfoot accuracies. You were on the right track, however you need to create a group and add stations to the group (choose select, new, add +). 1 station within 50 miles or 3 or more within 125 miles. I find better accuracies with 3 stations spread out around the data. You could be degrading the accuracy of your data when using Standard Code Processing with a Trimble H-star receiver.
Good Luck