What Should I chose for my activity level

The activity level here on MFP is described as follows:
Sedentary: Spend most of the day sitting (e.g. bank teller, desk job)
Lightly Active: Spend a good part of the day on your feet (e.g. teacher, salesperson)
Active: Spend a good part of the day doing some physical activity (e.g. food server, postal carrier)
Very Active: Spend most of the day doing heavy physical activity (e.g. bike messenger, carpenter)

So, in your case, I'd go with "active".
Any exercise you may do outside your regular daily activity (=work) is supposed to be logged separately, if and when it exists.

For comparison, I have a desk job, and I average around 10k steps a day on my walks (purposeful exercise). Therefore, I chose "sedentary" for my activity level, but I log all my walks (and other workouts) on the exercise tab.