File Sharing with Wireless N Portable Router & WiFi Range Extender

I'm having trouble setting up a wireless network and have tried
everything, so if someone can provide the steps, I would appreciate
it.

I am using a Cradlepoint CTR35 Wireless N Portable Router with a
Verizon 4G USB modem attached and a Netgear WN2000RPT WiFi Range
Extender. I have 3 computers all with Windows 7 Home Premium 32-bit. 2
computers can connect to the wireless broadcast by the CTR and the 3rd
can assess the wireless broadcast of the range extender. I've tried
setting up a Homegroup but the 3rd computer can't access any of the
files shared on computer 1, even though computer 1 shows up in the
network and password sharing is turned off. All computers have the
same time and are Home networks

I've also tried it without the homegroup but computers 2 & 3 can
access the shared files on computer 1 only temporarily, then their
wireless connections show "no internet access" and the network
disappears.

What is the best way to set this up?