Replicating Data From a Locked Down Data Set (Accelo Power BI App)

If I'm working with a Power BI application that a 3rd party has created, this application is locked down (Accelo Power BI App), is there a way I can take the underlying data and reflect it into a custom data store that would allow me to have greater flexibility over what I do with that data? I need to add some custom tables so that I can do some joins and calculations off of them. For example, I need to calculate utilization rate, which is based on the number of employees we have and the number of work hours available in a month. In 

I then need to use this table as a reference to calculate utilization both at an organizational level and individual level. The big problem I am having though is that I can't add any tables to the app that I am using because it's locked down by Accelo and I'm trying not to do a custom integration against their API and do it all from scratch. That defeats the whole purpose of them offering this Power BI app. Their underlying data model is attrocious so I need to be able to create my own tables and my own joins to get the data I need.