computers connected to Netgear switch Model GS308 cannot access internet

I've connected a Netgear Gs308 switch to the ethernet port of an Arris non-wifi telephony modem Model TM822R using a Cat-5e cable. Then I connected an iMac desktop computer (2011)  into one of the switch ports, and a Dell PC laptop (2007) into another port. The computers cannot acces the internet together. The switch only works for one computer only. 

 

If I connect each computer directly into the Arris one port ethernet modem, they work but of course I can only use one computer at a time; thus, the reason for purchasing the Netgear switch. Any ideas before I return this equipment? Thank you.