Before putting up any curtains, the most important thing is preparation. You will need to ensure that you know the correct sizes you will be needing and decide which type of curtain fixture you prefer or is necessary, pole or track. So the first thing you would need to do is measure the width of the window recess and then add 30cm (15cm per side) as the pole or track will need to extend past the window recess width. This will ensure that it blocks out more light when the curtains are closed.
Before installing a curtain track or pole, you will also need to measure 12-15cm above the window recess so as to mark out where the pole should go. If using a curtain pole, you will also need to measure where the end brackets will need to be as curtain poles also have decorative end pieces. To do this, take the total measurement from the fist step, and then at either end, go towards the centre 10cm to mark where the brackets should be placed.
Ensuring that you follow the correct steps for measuring for your curtain rods or poles can make this process much easier.