Good question. All team members need to be added to the submission by the deadline because all members must be eligible to participate. However, if you start the submission on behalf of the team, you'll be able to either add their email addresses to invite them or send them a special link that they can follow to add them. You can do that today and then continue updating your submission form until the deadline.
I am not seeing any option yet to add my team members or invite them into this hackathon. Am i missing something, i mean will the option be available only when i am submitting the project?
Yes, you'll see it on the submission form so if you start your form, you'll see a section called Team. That will have a link you can share with your teammates or you can add their email addresses to send an invitation.
You can continue editing the submission until the deadline, too.
Let me know if you're still having trouble!