Look at the recommendations for your age, gender, etc your cardiologist should also give you a target, mine (I'm 60, male) for example is around 120/70 on average, having a few measurements above 120 is OK but the average over a period of time should be close to the target.

There have been a discussion in this forum about how long to wait before starting to take your BP, like most people, if I take it immediately after going downstairs in my house it will be higher than expected. I normally wait for about 10-15 min. I also use a device that takes 3 measurements and provides the average, 30 seconds between measurements. I often notice that my last measurement is lower than the first, and that is normal I have been at rest longer. If interested the device is an Omron, it also connects to an app in my phone and maintains all the records for me, I can then export them to a report and send them to my cardiologist/PCP when needed. The report will show all the individual measurements as well as the average. The app also allows you to enter manually taken BPs for when I use a different device.