Altium Designer PCB Editor Set Component Reference Point Snap
Just drag the component by the pad (left click and hold on the pad), this will make the pad snap to grids and other references. If that is not working for you, take a look at the preferences.

Snap To Center
Enable to have the cursor jump automatically to a defined reference point on the object when you select it and be "held" by that point as you reposition it. When moving a free pad or via, the cursor will snap to the center of the object. When moving a component, the cursor snaps to the reference point of the component. When moving a track segment, the cursor snaps to the vertex point. If this option is disabled, objects will be "held" by the point at which you click on them.

Smart Component Snap
Enable so that when you click to select a component, the cross hair cursor appears on the nearest pad of this associated component in respect to where the cursor is. Disable this option so that the cross hair cursor always appears on the pad reference point of this component when it is clicked on.