You have to create an API request.
Here is the doc
all the examples you will find use curl, which basically encodes and concatenates the body in the url
http://ip:port/query?q=<InfluxQL query>
note that the query text is InfluxQL encoded as an URL (I’m not sure powerbi will encode it, but if not, you can encode the string yourself)
and since you are using PowerBI this might be useful (to avoid json parsing)