Promote your app with a quick microsite - Great for giving people a quick overview!
An example of a great microsite is path - https://path.com
Notice that what this site does well is to cleanly outline what the app does without making you scroll too much. I would say that one improvement path could make it to have a larger button leading to the app download, especially at the bottom of the page.
"But Michael!" I hear you cry - "do you have any idea how busy I am? I would love to be making sites left right and centre but I have my social media, webpage, clients and prospects to worry about! Where do you think I can find time to make an app???"
There are a few ways to make quick webpages but one of the QUICKEST is adobe spark. https://spark.adobe.com/about/page
if you're a big business then of course you probably have the resources to get a professional microsite done.
If you're a one man army - spark is a great. You can make a quick site in about 15 mins. A good site in about 30 mins.