Include Site Certificate when using HTTPClient

I'm trying to write a BR that returns data using HTTPClient. I've tested out the api.open-meteo.com example and can successfully pull data from this site.

The site that I am trying to query requires a site certificate for authentication and I'm not sure how to tell my BR to use the site certificate that is already installed on the SIC server. On the SIC server, I can manually run the query to the source site via a web browser which prompts me to select the appropriate certificate. 

Has anyone been able to include a site certificate to a HTTPClient request?

Thanks,

Cosimo