Chain Saws are Very Dangerous even if you have the user manual.
Your question is about the most scary I have seen on here...
It is not difficult - there must somehow, on all chainsaws, be a method of adjusting the chain tension.
There must somehow, on all chainsaws, be a method of removing the chain.
It will be very, very similar on all chainsaws - a cover over the drive end of the chain will need to be removed.
A child should be able to show you where the cover is.
There will be an obvious tension adjuster - I set mine to about 3mm play with a cold chain. The chain bar can be reversed - as in turned upside down - on most saws to even out wear. The oil holes should be clear of sawdust and the oil reservior have oil in it.
Take care...
Peccavi, July 2010