If it is the older style with a long rather than wide firebox,
and tiles along the side, then the following should get you
started. It may also be relevant to later models …

The lever above the door that moves sideways controls the damper
at the rear of the firebox, which has to be to the right (opens the
damper and moves an interlock metal tab to the right) to allow the
door to be opened. The small lever at the top front on the right
hand side sets the air intake in 3 steps, to the rear for maximum
air, to the front for minimum. When the damper opens the interlock
mentioned above should pop the intake lever back to maximum.

I have experienced 2 well used units, and the damper lever
linkages on both have been in bad shape. This means to close the
damper (lever to left) properly may require a bit of technique, see
below.

To start, damper lever to right, open door; my technique is to
feed in plenty of screwed up paper, then a layer of twigs or
kindling, then a couple of decent bits of timber on top. At the
very last, a few screwed up sheets of newspaper at the very front
filling up the door, gets everything happening fast. Light this
newspaper in a couple of places, then immediately almost fully
close the door, leaving it ajar about 3cms of so. The fire should
take off like a rocket; move the door in or out to adjust how
ferocious it is. What you want is for the chimney at the base to
get pretty hot, and to see that decent pieces of timber are well
and truly burning. Then close the door properly, using the lever;
don’t over-tighten as the catch is a bit flimsy and will bend if
you overdo it.

At this point the damper is open, air intake is maximum. As soon
as the fire appears to be really stable close the damper, which may
need some fiddling — to do this, move the lever to the left, then
slide the interlock tab with your finger to the left, then move the
lever again to the left with a bit of a jerk. When the damper
closes properly it will make a bit of a clang; if your unit has
this problem you’ll probably have to experiment a bit to get the
technique right.

If the fire dies down at this point you’ve been too eager to
close the damper: damper lever to right, open the door a touch to
get it going once more, and try again.

With the damper closed the wood is being burnt in the most
efficient way, giving off the most heat for the wood used; the only
thing to worry about then is the air intake. Lever to the back for
maximum heat, towards the front slows the burning rate, and if you
fill the firebox last thing at night the front setting should give
you a still usable fire in the morning!

Depending upon the type of wood burning and the air intake
setting, you need to be careful opening the door: do it too quickly
and you will have smoke pouring out into the room! Only open it a
few cms or so initially, and leave the fire to stabilise a bit
before opening further. This is also the way to get the fire going
again if it suffocates (firebox fills with smoke)

Good luck!

Frank