make a PSTN call from softphone using IP PBX module

I just bought a PBX IP Module running Linux IP PBX 2.6 Unitekk i succeed to run voip call in my lAN network and also getting the PSTN call into my softphone (XLITE) but i can make an externall call using my softphone through my PSTN line Can anyone help me to find the right configuration into my inbooud roules or trunks i dont know just give me a solution to my probleme thanks in advance