Daffid, if you lay a 4stroke down the wrong way the sump oil can get back into the cylinders and then when you try to start it you are trying to compress oil rather than fuel/air mixture - which won't happen - so best case you can't turn over the engine and worst case you bend bits of metal and cost yourself a lot.
The good news is that normally you can lie a 4 stroke engine down just only in certain ways. The manual should make this clear (although I think they could do with some brightly coloured stickers on the actual engines). If you do lie the engine down wrong its not automatically a problem - stand the engine up right, remove the spark plugs, turn it over by hand a few times, clean and refit the plugs, check and top up oil level and off you go.
I am guessing you are going to do a PB level 2 course to get you started - and good training centre should be able to spend 10 minutes with you to demonstrate that procedure.