To install:

1. Find the directory where Stardew Valley is installed.  For the Steam version, open Steam, find Stardew Valley in your library, right click, select Properties, go to Local Files and click Browse Local Files. From there, go to Contents/Resources/Content/Strings.

2. Find the original Events.xnb and rename it to something like Events_old.xnb.

3. Extract the modded Events.xnb and move it to the Strings folder.

4. Enjoy!