You need to use the command line and the
adb tool.
Have a look on Google for various techniques - not all are guaranteed to work so you'll have to experiment until you find one that does:
https://www.google.co.uk/search?q=android+emulator+adb+push+to+sd+card&ie=UTF-8&oe=UTF-8.
Watch that if your OSMDroid uses the MyLocationOverlay it will possibly crash on the emulator when the app tries to enables sensors.
I gave up using the emulator when testing MyLocationOverlay apps but i see a possible workaround.
Open AVD Manager and select your virtual device.
Click Edit.
Now under the Hardware section you can click New and a dialog opens.
In the dialog is a Property drop down list where you can set or enable various hardware settings in the virtual device.
If you add GPS support and/or Magnetic field support then the virtual device might be configured with software emulation for the sensors and no longer crash.
This is on my list of things to do so may or may not work.
Note that i have found that if you change any settings in the Hardware dialog then the next time you start the virtual device all installed apps will be gone - it looks like changing a Hardware setting causes a device reset.
Have a look through the other available options - you can set device RAM size and density and some other values too which might be useful.
Martin.