This is the grid pattern at its simplest, so your horse starts to learn and builds confidence. Set it up as shown below with a ground pole (a), cross-pole (b) and then a vertical (c). There should be a one-stride distance in between each fence.
l1 In an active trot with plenty of forwardness, ride towards the centre of the ground pole. l2 Ride straight to the cross-pole and then the vertical, keeping your horse in the centre of each fence. l3 Repeat on the other rein.
If your horse has a tendency to rush, you could add another ground pole halfway between the cross-pole and the vertical. To progress, gradually increase the size of the vertical.