You can add scoring points on many different places in Marketo.
I like to do it on a specific lead scoring program and have all the values of my scoring model in one place, this is why I really like using tokens for the values.
So how to do it?
1. Go to My Tokens section at your folder level or program level. I personally like to do it at the program level.
2. Create a new Score Token and add your values. Create as many as you need
3. At your campaign level, in the flow select the token that you have created (instead of entering a number).
Easy peasy! Now you have all your scoring values in a centralized place.
Note: If you modify the values the new values will affect new leads affected by this campaign. Old values will remain for leads that were affected by this campaign in the past.