if you are using a magic, upright spins are easier to do. get some altitude, start a spiral spin to the left or right (i usually go left) left rudder,left aileron , full up elevator, half throtle or less. After a spin or two flaten out the wings with neuteral or a little right aileron (still holding up elevator and full left rudder) the plane will break into a tight flat spin. to exit just release the sticks.

if it still is spiralling nose down you may be too nose heavy or you don't have enough elevator to lower the tail. beware of too tail heavy, it can make exiting the spin harder.

if it tumbles rather than spins you are using too much elevator.

Once you are in a flat spin adding more throttle will make it spin faster and slow the decent