You will be able to gradually reduce height as you become more proficient at each manoeuvre.

Loops
The loop is probably the easiest and therefore the first manoeuvre to try.

Start with the model flying at a safe height, into wind and with plenty of forward speed. When the model is passing in front of you apply up elevator (back cyclic) to start the climb into the loop, (not to much up elevator or the model will come to a stop) as the model reaches the inverted section pull a little more up elevator and keep it there until it gets to the bottom of the loop. Your first loops will probably be more like a figure 9 but if you lower the collective pitch to negative at the top of the loop you will gradually make the loop more circular.

Stall Turns
As with the loop pull back on the elevator to start the climb, as soon as the model is in a vertical climb reduce the collective pitch to 0 degrees, when the model comes to a stop apply full rudder left or right. You are now in a vertical dive don't panic! This is where the safe height comes in; just apply up elevator to get the model back to forward flight.

Rolls
The first roll will take a bit of nerve but once you have started just keep the stick over until the model returns to normal flight.

Again with plenty of height and forward speed apply full right or left cyclic, as soon as the model starts to roll apply 0 degrees pitch followed by negative pitch at the inverted section followed by 0 degrees and then back to normal. The timing of the pitch inputs are critical and your first rolls will probably be more like a barrel roll but just keep practising.

Most other aerobatic manoeuvres are really just combinations of the above so I will not go through them.

Its not getting the manoeuvres right every time that's important, its regaining control when it all goes wrong that really matters.