This can unfortunately be quite a fiddly process.
if you are removing the female coupling to allow for the use of the hose directly into the hose real, or otherwise are not worried about using or reusing the female coupling once it is removed, it can often be easier and less time consuming to simply break the coupling off of the hose.
If the original hose is to be used further as an extension hose or you wish to reuse the coupling, we reccomend the proceedure to avoid the damaging the coupling:
Use a flat screwdriver to press against the underside of the spring pin. Press gently and lightly. 
Hold the screwdriver against a table top or similar and apply light pressure to keep the spring pin pushed up agains the other side of the coupling. Now there are two small wings on the top of the coupling holding the spring pin in place (the pin should now be pushed up agains them) These are easily pushed inwards with another screwdriver, or in this example a knife (be careful when using sharps!) to allow the spring pin past and out of the coupling.
When the spring pin is fully pulled out you can pull the innermost sleeve down over the hose. A new u-pin appears, and this is the one that locks the innermost part onto the male coupling. This is easy to loosen with a flat screwdriver or similar using the small groove under the u-pin.
When the last pin is out, both sleeves can be pulled off and moved onto the hose you removed from
the drum.
To attach or reattach the female coupling, please pay attention to the correct attachment sequence of the parts:
The outer sleeve goes on first and down over the hose itself, before the innermost section is attached and locked in place with the U-pin. The outer sleeve can then be pulled back up and over the innermost part, and then appropriately positioned for the spring pin to be inserted.
Before putting the spring pin in place, pay attention to the position of the inner sleeve against the outer one so that the cotter pin will eventually fit into the slot: 
Give the cotter pin a little push so that it snaps into place behind the plastic lock pushed inwards earlier.
If you broke the outer part of the sleeve or anything else, you can order a new coupling in our spare parts shop at the following link: AVA female coupling