- Download the right version (DOS or Windows), see FAQ
- Unzip it into your TTD directory
- [Optional] Set up the new graphics, see New Graphics
- Run TTDPatch
Note that TTDPatch does not change any of TTD's files. You can write-protect the TTD executable to be sure. Instead, it will copy the old executable (either ttdx.exe, tycoon.exe or gamegfx.exe) to ttdload(W).ovl, and modify this copy only. You can switch between TTDPatch and the regular TTD at any time, simply by choosing which program you run. ttdpatch(W).exe is for running with the patch, and the regular ttdx.exe, tycoon.exe or gamegfx.exe for when you want the original TTD.
However, savegames that are saved while certain switches are activated may be incompatible with versions not running this patch. This also applies to scenarios created with the scenario editor. Incompatible savegames may cause TTD to crash, so be careful when loading games saved with the patch into TTD.