xlCompiler has optional feature - add End User License Agreement to spreadsheet.
To setup EULA options you need to open Compilation Options for your File or File Group.
To see EULA item on the left you need to select Activation Key protection option. EULA could be added if your spreadsheet has activation option.
You need to check option Show End User License Agreement on this page.
There is a secondary option Show EULA on each start. You need to check it if you want to show EULA every time your file is opened.
Last and the most important item - you should provide text for EULA.
This is described in the F.A.Q. topic - How to add EULA.