Someone help me please!!

steam group... then select for wich group your are part of will be.

Steam Group, matey!

Plus you need to be member of the group that you're choosing, and sync Steamgifts after joining/creating the group.

You can't make it like that. You can however make a group only giveaway and advertise it on the forums so people join

So i can select steam group so that people can only enter the giveaway if they join the group first??

As people have said, choose group giveaway. If you choose private, you have to manually give the link to each person you want to have access to the giveaway.