Express Train from Different Terminal of Capital Airport.

Hi there,

I will arrive T3 and my friend will arrive T2.
Unfortunately, my friend can not speak Mandarin at all and has limited English.
We will take Airport Express Train to Dongzhimen, together.
Is it possible for me to exit T3 and enter T2 to meet my friend and take train together from T2?
Or is there connecting way between T3 and T2, so we can buy ticket and taking train together?
Please kindly advise.

Thankyou & Regards,
Dwira