If they're in the lawn,you can't - just twist them off and dispose of them, they're the fruiting bodies of an underground root system which you can't see.
If they're in the border, do you have dead wood lying about, either in the form of old tree stumps, or decorative driftwood type stuff? Or have you used a lot of bark chips? Bark chips often produce mushrooms or toadstools, they're usually harmless. Mushrooms associated with old, dead wood may or may not be harmless, and removing the wood may solve the problem.

Bamboo I had lots appear in my lawn last year but so far this year it is clear of them. Is this because of the long dry spell?

Yes, I'd imagine so - though sometimes, if the turf was new, the mushrooms do pass after a time.

Thanks Bamboo