Get the files from our homepage (https://www.europabarbarorum.com/), the source you mentioned delivers an outdated installer.

Steps:
1. Just copy a clean RTW folder (meaning no personal changes or left-overs from your earlier attempts) to a backup folder, move or copy the original folder to C:\Games or another location outside Program Files.

2. Start the EB 1.1 installer and select your newly copied RTW folder as destination (in the installation progress you can select if you want to have additional things (Documentation, Recruitment Viewer and Trivial Script), you select all of them, they can be installed under Program Files without problems)

3. Start the EB 1.2 installer and select your newly copied RTW folder as destination

4. Download all fixes from here: https://forums.totalwar.org/vb/showthread.php?t=109936 and apply them as mentioned in the thread

5. Read the FAQ: https://forums.totalwar.org/vb/showthread.php?t=84854

6. Use 'EB-Singleplayer' found in the main RTW folder to start EB and enjoy!

If you have questions or anything is unclear, feel free to ask, but remember, I only can help you if you describe at which step problems occur...

XSamatan