APIC is available as a Chrome packaged App (Also works with Chrome OS), web app (to be used in a browser), Native app for Windows, Mac (coming soon) and Linux (Coming Soon). You can select any option that suites your need.
You can install APIC from Google Chrome's app store and launch it from Apps panel. To install APIC Chrome app, head over to Chromes's app store, click on the Add to chrome button and you are all set to go.
APIC also comes as native apps for windows (.exe), mac (.dmg) and a linux version coming very soon. You can download the native version here.
You can use APIC directly from your browser by visiting https://apic.app/app.
Warning: The web version of APIC (API testing module) suffers with the limitation of CORS where browsers don't allow access to resources of other domains unless the response contains Access-Control-Allow-Origin header with a value of "*" or "https://apic.app" (without the quotes). To overcome this issue you need to install a plugin that will allow APIC to access resources on other domains by adding Access-Control-Allow-Origin: * header. You can download the helper plugin for chrome from https://chrome.google.com/webstore/detail/apic-extension/dejjobgejdajdjjhjcindbjcfohoiehn
For Firefox/IE/Safari you can install equivalent plugins that allows modifying Access-Control-Allow-Origin header.
Before you start here's what APIC can do for you.