How to get the campaingns key?

Reading the documentations of the API, I see that is necessary have the campaign key, but I don't see how can I get it.

For example to get the campaign details we need to do the request:

https://campaigns.zoho.com/api/getcampaigndetails?authtoken=[API Authentication Token]&scope=CampaignsAPI&campaignkey=[campaignkey]

I have the API Authentication Token but I don`t see how to generate the campaignkey