You can heat up the pad itself and place the DMT on top and then place in the GVG, or you can drop some DMT onto the pad when it's in the GVG and then slowly inhale, watch and stop inhaling when the DMT is melted. Either way has worked fine for me. Sometimes its hard to get the pad out so I usually just use the latter method.
Start off small. Don't worry about the breakthrough. 20mg could provide a breakthrough. Start there and work your way up to what you like. I would think 20-30mg would be a good start point.
"In the universe there is an immeasurable, indescribable force which shamans call intent, and absolutely everything that exists in the entire cosmos is attached to intent by a connecting link." ~Carlos Castaneda