Not 100% sure what you mean by 'show begonias', but I think they're probably the tuberous rooted ones, which can be overwintered. Instructions in the link below, along with other info

https://www.rhs.org.uk/advice/profile?pid=815

Hya Thanks for your advice, i was told at the Garden Centre where i got them that they were Show Begonia's they grow like a little tree with lots of shoots coming of them and the Flowers are very Big, i was supposed to get Non Stop Begonia's but they said they must have got mixed up with the Orders, hope this helps, cheers

Not really - what would help is a photograph or two!