How can I append a query parameter in the Target Url

[#1]

I am a beginner in apigee.

I have a very basic question: I will have to append a query parameter in my target endpoint URL.

For example: A Get operation

http://abc-company-api/v1/data/sales?authcode=yuozerrt

Also please note, this is not a dynamic parameter. It will remain same until my vendor changes it. My questions:

1. how should I add this authcode query parameter when I consume the target endpoint? This is not a header parameter.
2. What is the best practice when deal with similar type of query parameter.

Thank you.