Get an alarm bracelet or necklace from whoever supplies them in Britain or wherever you live. I know they are available in Scotland.
Failing being supplied with one, take your mobile with you at all times, making sure it is fully charged.
It depends how you landed when you fell, and on your weight and physical strength in arms and legs, how you can get up unaided.
If you land on hands and knees and can't get up from that position, try sitting down on your bottom and pushing yourself up using your feet place flat on the ground with your knees bent and a hand flat on the ground on either side of you.
If that is no go, then either shuffling on your bottom, the way we came downstairs as toddlers, or crawling on your stomach as we did when playing Indians (oops, sorry Native Americans! Now doesn't that look ridiculous? ) as children until you reach something you can pull yourself up by.
If none of this is possible, which I can well imagine to be the case, yell loudly until someone comes.
It would make good sense if we all, me included, practised some of this on a nice soft carpet at home to find out what works.
In the snow and ice we have had for the past fortnight, I take a stick with me when I go out, although I do not usually use a walking-stick, but one does provide more stability on slippy or rough ground.