Some Mac computers won't automatically open database export files in EndNote X8, such as .ris and .enw file types, and ask you to browse to the application every time you try to open them. Follow these steps for each different file type that you want to open automatically in EndNote X8:
Download the .ris or .enw file to your computer
Right-click (or Ctrl+click with Apple mouse) on the file and select Get Info
Under Open with: choose Other...
Browse to EndNote X8 in the Applications folder > tick Always Open With > click Add
You will return to the info box for the file, and you should see EndNote X8 selected under Open with:
Click Change All... so that EndNote X8 is selected for all files of this file type, and click Continue to confirm