Ads API Target Custom Audience to Specific Campaign

[Manjunathk707]

How to add Custom Audiences to particular Campaign?
Use case : We have list users that i want to push to Twitter Ads using Ads API. there is a way to to add custom audiences using Post API call (accounts/:account_id/custom_audiences/:custom_audience_id/users)
Questions

1. Where does these data stores
2. If account is having multiple campaigns, then for which campaign these audience will be targeted
3. If i want to target my audience to particular Campaign using API, how can i do this?