I'm trying to build call performance dashboard using Power BI with RingCentral API data, I'm having developer console account created a APP with my credentials. Now how to get the API data 
I am not an expert in Power BI so I cannot help at the code level. But RingCentral API platform is a REST API platform so you can use an HTTP client to call the APIs. You first need to authenticate a user and get the access token, then use the access token to call other APIs.
Maybe this YouTube video could help you get started.
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