If you got an electronic visa i.e. your visa is on your Atlys app and consists of a unique code then there are 2 ways for you to have your airline verify your visa:
1. Show at check-in: you may show the visa physically at check-in on the day of the flight.
2. Upload to United's Travel Ready Center: you can take a screenshot of the first page of your visa, and upload it to United Airlines' travel-ready center here. Note that you may still be required to show your visa in person during check-in.