Hi,
Based on my understanding, as Damian mentioned Prism should not introduce any difference from the approach mentioned in this article.
In Prism, you can create and set a new instance of your HttpClient, and make further calls in your applications without problems. This approach could be implemented in any part of your application.
The only difference you may find when using Prism, is that in case you want to share the same HttpClient instance, in order to consume it in a loosely coupled component, you may have to implement the logic to pass this instance, for example by benefiting of dependency injection containers or shared services as mentioned above.
Please, let us know if you have any issues when following this approach.
Regards,
Agustin Adami
http://blogs.southworks.net/aadami