Hi, I am a complete beginner to stata and need help with creating a new variable.

I am trying to make long term conditions into new variables, for example, one would be a variable for Atrial Fibrillation so that I can then filter through my data to see who has it and who doesn't. I tried to use g Atrial Fibrillation = 0, but then I got a message saying "too many variables specified" so I'm not sure what to do now.

Any help would be useful, thank you!