You will need at least version BFME 1.03 to run this mod.
Versions after this such as 1.04, 1.05 and 1.06 will work fine since the launcher bypasses those patches.
You'll also need Java installed and up to date.
If you have Winrar installed make sure it is not set to run .jar files or running the launcher will just open the jar file instead of running it.
If clicking Play doesn't work for you then you've got 2 options.
First is to disable admin mode for the file lotrbfme.exe.
To do this go into properties for lotrbfme.exe then disable Run as Administrator.
Option 2 is to use the Set up button which should set up the mod files, then just run the normal game launcher while keeping the ROS launcher open.
Launching Vanilla Issue
If the normal game is launching when pressing Play then your issue is file permissions.
Go to your game folder and right click then go in to Properties>Security and set the permissions so that your user account and the admin account have full control.
Read this first before posting in comments or discord since my time is limited I'd rather not have to answer the same questions 3 times a day.
To test whether you've actually read this first if you have an issue use the word Acorn so I know you've read this.