I was looking into the wiki and could not find much information on the topic. I'm not asking for code, just asking for a push in the right direction.
I've answered a question similar to this.
After checking the wiki I found this.
script.Parent.BodyForce.force = Vector3.new(0, game.Workspace.Gravity, 0) * script.Parent:GetMass()
You could do an if statement,
if game.LocalPlayer.Character.HumanoidRootPart.Position.Y:GetPropertyChangedSignal() then game.LocalPlayer.Character.BodyForce.force = Vector3.new(0, game.Workspace.Gravity, 0) * game.LocalPlayer.Character.Parent:GetMass() end