If you are unable to perform one pull up these are the intermediate steps between Body Weight Rows and and achieving your first Pull-Up. All of these progressions should be performed with the technique described in the full pull up.
Stand on a platform where you can get your chest to the bar. You can use either a pull-up or chin-up grip. Step of the platform and slowly lower down. Make sure that you control the decent, don’t just drop into a dead hang. If you are struggling to control the decent keep one foot on the platform and use it as a brake to slow your decent. As your strength increases you will need to use your leg less. Once you can control the decent through the full range of motion, try pausing half way down for a few seconds then continuing to descend smoothly.