Old patternmaker learning new tricks

I'm trying to extract the interior of a casting model to see what the  foundry core will look like. I placed the casting model into an assembly and inserted a block into the assembly. I edited the block so its coincident to the faces that the core comes thru. My problem is my mold tool bar won't turn on nor does it let me go to "insert/ feature/combine. What am I doing wrong?

Patternmaker

SolidworksPlastics And Mold Design