New user with dumb questions

I don't think you can. You can add manuka workouts etc. not steps..so if your looking to add the calories for the steps. Add a manual workout with the calories off your other device to your dashboard on here. That way you get the calories for your steps added to you eating etc

Speaking as a long-time MFP user, I think you have two - maybe 3 - general options, and you can use a combination of them if that's most appropriate.

Let's make a distinction between walking that's incidental to daily life, and intentional walks to add steps/exercise.

If the walking is incidental to daily life - job, shopping, home chores - a good option is to look at the averages over time, and set MFP activity level to provide some calories to support that daily life.

If the walking is intentional walks to add steps/exercise - just going out and walking for X amount of time - then logging that as exercise may be a better option.

Overall, if you watch gives you a total calorie estimate for everything you do in a day, including just being alive and breathing, you could also manually set your MFP calorie goal based on that value, ideally averaging the watch's data over at least a week of your typical schedule. To generate weight loss, you'd knock off 500 calories daily for each pound a week you want to lose weekly, or 1100 calories daily for each kilogram you want to lose weekly, using arithmetic to adjust for fractional pounds/kilos.

As a variation on that theme, you could simply look at your watch's total calorie burn on Tuesday, and make that the basis of your goal on Wednesday, using the same calorie math as mentioned above to create a deficit if your goal is weight loss. Basically, that would be manually simulating what linking a tracker does, but on a one-day delay. Even with the one-day delay, the long run results for body weight would come out the same.