Welcome to the forum. Well when I shorten my chain, I did not have a chain breaker, so I ground down the link using a cut off wheel and then a pin punch. Breaker would have been easyer. The master link must go between two of the narrow links and the retaining clip must slide on oppset the direction of rotation so it does not get knocked off. There are directions for assembling these bikes on many of the web sites like the ones that have ads here Page Title
is one of them. And there are many people on this forum smarter then me who can help you out if you get stuck. Have fun building.