WCF chap XIX : 1 says: God gave to Adam a law, as a covenant of works........

Genesis chap 2:16 says :And the Lord God commanded the man, saying........though shalt not eat of it.

How is this "command" a "covenant" ?

If it is a covenant,how is it a covenant of works ?

WCF XIX:2 says : This law....was delivered by God upon Mt Sinai.

Deuteronomy 5:2 says : The Lord our God made a covenant with us in Horeb.The Lord made not this covenant with our fathers, but with us,even us, who are all of us here alive this day.

Does the "us" include Adam ?