First step is to configure your ATA to use Voxalot. This tutorial should help:
VoXaLot
To test your setup dial *600 (echo test)
Then you need to add sipgate as a provider within Voxalot. See:
VoXaLot
At this point you should be able to make calls via sipgate. Then you can get more advanced and customise dial plans.
This should get you started.