1.Right-click on a file that uses the file type you'd like to change the default for. For example, one with a .jpg extension (a photo).
2.Click on Get Info in the pop-up.
3.Click Open With if the section isn't already expanded.
4.Click the dropdown and choose the citrix app. (Example image shows changing to Photoshop for file type .jpg)
5.Click Change All...
6.Click Continue when the Finder asks you if you're sure.
7.Now any time you open a file with that extension, the Finder will automatically open it with the app you've selected.