POST TRANSLATIONS REQUESTS HERE

Can someone please explain me the grammar in the following sentence (From League of Legends) :

ランダムに選出されるチャンピオンでチームを編成し、
敵のネクサスを破壊しましょう。

I know it roughly means something like
"Your team is composed of randomly selected champions, and let's destroy the opponent's nexus"
Can anyone give a more accurate translation ?

And my grammar question is about the following :

チームを編成し
why isn't it チームを編成するし　?

Thanks in advance !