Hi,
If you have two cnns, you can simply do:
inp = # Your input
out1 = cnn1(inp)
out2 = cnn2(inp)
full_out = torch.cat([out1, ou2], dim=1) # dim=1 is the channel dimension for 2D images
full_out = full_out.view(full_out.size(0), -1) # Linearize for the FC
res = fc(full_out)

Does that work for you?