One of the great options in Office 365 SharePoint online is that if you find some apps in your SharePoint store and want to use that within your sites, (why? well, cause you want youtube search/copy paste documents/world clock/weather…you get the idea), you can search for the app you want in your Site Contents ->Add an app. If a matching app is available in SharePoint Store, SharePoint lists it and provides a hyperlink to the store.
Then on its as simple as selecting the app and requesting it. Your job is done.
The Company Administrator then has the task to add the app to your sites for consumption. (If auto install is disabled in your environment. If it is not, it SHOULD be. Filtering what app gets added to your Office 365 SharePoint environment is a MUST in my opinion).
So, now over to your CA. She logs into SharePoint Admin Center->App Catalog->App requests->Edits the requested item and proceeds to get and add to sites. Thats it and you can see the step by step screen shot of the process below!
Now, Install responsibly! 😉