When creating a Population Tool Locator using the Population Tool Context, connections between the new Population Tool Locator and Entity Types / Terrain /... are automatically created.
However if you want to add or modify the process of these connections, you can overwrite the following function:
glmPopToolHandleConnections(string popToolNode, string connectedEntityTypes[], string inMesh)
This function is located in glmPopulationToolUtils.mel file in the Golaem scripts directory.