How do I put the chain back on? electric?

There should be a tensioning wheel that takes up the slack. On my cheap, electric chainsaw it pokes through a cutout in the cover - runs vertically. With the machine unplugged and the cover off it is very easy to adjust - when the cover is screwed on it beccones a little more difficult to move.
My handbook says adjust for 3mm play in the chain. What does your handbook say?

Richard Buxton
September 2008