To do so, click your Publisher Name at the top of the account (next to the silhouette icon). In the side-bar at the left, look for "Defaults for New Titles" and click the orange arrow next to "Region"
Select your preferred regions. If you prefer to receive requests from members throughout the world (no preference), please leave all the boxes blank.
Members browsing FIND TITLES will see your preferences displayed next to the Request button on the title record, like this:
You can change the preferred region settings for an individual title from the Title Details page, for any title.