The RG170 and RG360 are both limited devices and as such, they are unable to access Google Mobile Services (GMS) or the Google Play Store.
As such, you will not be able to download applications the traditional way. Instead, you can do the following:
1. Retrieve applications in APK (Android Application Package) most times from the applications website.
2. From there, place the APK on a correctly formatted SD card.
3. Insert that card into the device.
4. Select the APK from there and install directly to the device.
Please note that this device has limited internal memory and that using it all with applications such as Facebook can affect the performance of the device.