From the menu on the left, choose Markers from the main dropdown menu. Start with Add Island Marker, the icon on the top right, and left click on the middle of your island. Then, left click and hold on the Commander icon to the North of the mainland (it looks like a Darwinian) and drag it down onto the island. Select the Add Hydrocarbon icon (the yellow one) and place a couple of them on the island, followed by four Mass points (the green icon).