If you are using an external audio interface, you can use the local IO to pass signals from the GLD to this interface and back form the interface to the GLD.
The output sockets of the GLD which are connected to the interface can be assigned to the outputs of mixbusses (post fader) which are used as send busses for the external FX. The returning signals which are coming to input sockets oft the GLD can be assigned to channels to be mixed together with the rest of the channels.
This is quite the same procedure as you will do when you connect an external multi effect processor.
On the Laptop I would prefer to you an VST Host like the Waves MultiRack, or LiveProfessor. There are also freely available VST Hosts. But for the first steps it would be possible to use a DAW to do that job. In this software you have to load the favorite Reverb plugin and connect that plugin to the inputs and outputs of your interface.
Then send signals to the computer, tweak the parameters of the reverb as you like and listen;-)
I am afraid that more detailed instructions needs the information which Computer, Interface and software you want to use.
