Setting your position without a GPS (or with a disabled GPS) is really easy. Just do the following steps:
0) Ensure that Enables / Beaconing Enabled is checked.
1) Ensure that Screen / Tracking / Me and Screen / Tracking / Locked are both checked. This isn't actually required, but it gives you a nice black dot at the dead center of the screen as you…
2) Drag (Pan) and zoom the map until the center is where you'd like your station to be and then…
3) Zoom in even closer just to make sure you're on the right spot and then…
4) Click Transmit and answer Yes to the question "Move ME To Center?".
Your saved location will be moved, your station will move, and a beacon with the new location will be sent to APRS-IS (and RF if configured and enabled). Note that if you do this too quickly and move too far, sites like aprs.fi might reject your updates. Just wait a while and let your Configure / Genius / Max Time beacons continue insisting on the current location and eventually they'll decide to agree with what you're beaconing.
Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32