Cursor

Sounds like you haven't already entered notes or rests into the measure? In that case, indeed, the cursor has nowhere to be - it only moves to positions where there are notes or rests, since music is read and written left to right. If you're saying you want a rest or two in the measure, no need to enter notes and then delete them - just enter the rests directly. Right-click if you're using the mouse, "0" if the keyboard. See the Handbook under note input for more info on how that all works.