As a rule of thumb, the best time to move a hardy fuchsia plant is when the leaves fall off and blooms are spent. However, transplanting fuchsia plants with foliage, and even with blooms intact, is often successful.

You can transfer them from a pot at any time of year, as long as you don't disturb the roots. Summer is best, because they will have a chance to settle in before the winter comes.
Just make a hole in the ground, tip it out of the pot and pop it in the hole.

The best time to move ones growing in the ground is after the leaves have fallen ...

You have to make sure you have hardy varieties though, because many are frost tender and won't last the winter outside.

If the ones you bought were only plugs, maybe you should wait until they are much bigger before planting them out.

Here's a tip for you - when you plant a hardy Fuchsia, make sure you plant it deeply, so that some of the stems are below the ground.
This will give them some protection from the worst frost, and ensure their survival in a hard winter.

Also give them a mulch in the winter, for a bit of extra protection.
Most hardy ones will survive though :)

If you are not sure whether they are hardy or not have a look on the British Fuchsia Society's website - they have a long list of all the hardy varieties marked with stars to show how hardy (or not) they are.

Thank you all very much for your replies and advice, which I will act on.

Helen