Clean the wheel using 3M Grey Scotch-brite™ and warm soapy water to remove brake dust /road grime etc.
If possible push the tyre away from the rim to give better access to the damage.
Sand out the defects using 3M™ Hookit™ P180, P320 then P500 disc. This is better done using either the 76mm or 125mm size abrasive. (N.B. Care MUST be taken around the ‘spokes’ not to alter the shape.)