Your panel is only 100 amp max. Looks like you have no more room for a 240v circuit. A 240v circuit requires a double pole breaker, or in your panel's case, double pole fuse. These are the black rectangles in your panel.
I would recommend upgrading your panel to a 200amp unit. This will allow you to use breakers vs fuses.
hi all the black rectangle 230v 30a spots are unused expect the one that says AC
Do you have an electric stove/range? electric water heater? electric furnace for heat? electric clothes dryer? All of these use 240v