To begin with, please check for any available updates for your phone and Galaxy Watch. On the phone itself, go to Settings > Software Updates, and for the watch, please open the Galaxy Wearables app and go to About Watch > Update Watch Software > Update Now. Once complete, head to the Galaxy Store and search for Samsung Health Monitor to gain access to the Blood Pressure Monitor and ECG features. Please note that this is only available for the Galaxy Watch 3 and Galaxy Watch Active 2. To find out more, please check the link below.