Sure, just follow these simple instructions to add your Textfree Number to your Google Voice account.

Note:  You must have Textfree with Voice in order for these instructions to work.  If you don't have Textfree with Voice enabled, you can upgrade or use the instructions located here: Google Voice without Textfree Number.

1.  To add your Textfree Number to your Google Voice Settings:

a.  Go to Settings in the upper right hand side of your Google Voice screen and select Voice Settings.
b.  Click on "Add a new phone" in the Phones tab.
c.  Enter a name, your Textfree Number, and select "Mobile" as the Phone Type.
 d.  If you would like to forward text messages sent to your Google Voice account to Textfree with Voice as well, keep the "Text Settings" box checked.

e.  Click on Save and you will be asked to verify your phone.  Click "Connect" and Google Voice will make a call to your Textfree Phone Number and you
     will be asked to enter the 2 digits displayed in a pop box like the one below using the keypad in Textfree with Voice.

f.  When you have completed the verification step, you will see your Textfree number in your Google Voice settings.

Google Voice calls and text messages will now be forwarded to your Textfree account!