Issues with Dell Streak

Since I have been unable to get access to the XCSoar forum thus far, I thought I'd go ahead and post my questions here.

I just got a used Dell Streak 5 that was previously an AT&T one.
It appears it is Android 1.6 and seems to be functioning fine.
I attempted to install XCSoar using wifi.
I first tried to install it by downloading the file its3elf but it won't let me install an app that isn't from google play. It also do not see an option to allow it to get apps from other sources.
I then tried to download it from google play. Google play tried to pull up the 'terms and conditions' web page but it appears the browser is no longer valid and won't let me go further.

What's next?
I have no SIM card for it but if I'm using wifi, I shouldn't need one, correct?
Being new to Android, does it require that I get something like "CM7" or "fastboot" or something else?

I assume that I have to either make the phone capable of accessing google play normally or I have to find a way to install XCSoar from a desktop?

Will any of the changes interfere with the functionality of XCSoar and what it needs to operate (IE Bluetooth to connect with my vario).

ANY ADVICE GREATLY APPRECIATED!!
Wade