Drill the necessary holes & insert wall plugs (recommended 5.5mm drill bits for 6mm wall plugs or use 5mm drill bits for 5 / 35 hilti nail).
Insert the screw / hilti through bracket fixing hole and tighten firmly.
Position the head rail up into the bracket and turn the wingnut washer tight ( NB : Not all head rails will be supplied with brackets eg : bamboo blinds without valances will use a plug and screw or hilti nail ).
For cordlock system, unlock the blind by pulling cord to the centre of the blind and slowly let go of the cord until the blind reaches the sill or required length.