The zip file contains a mod folder called my_mod which should be installed in the Rome - Total War directory. So in there you will have directories:
Create a new desktop shortcut to your RTW or BI.exe, right click it and select 'properties' add a space and '-mod:my_mod'
after the last " in the target line (and preferably add -show_err as well) so line looks like:
"C:activisionRome - Total WarRomeTW-BI.exe" -mod:my_mod -show_err
For RTW play the imperial_campaign option, if using the BI.exe access the imperial_campaign through the
provincial campaign menu.
NOTE: Custom battles can not be played when using the BI.exe this is not a problem with the files themselves it is a known issue that there are difficulties in setting up custom battles in RTW mod-folder to run under BI.exe.
(Historical battles and rise_of_rome provincial campaigns etc. are not included)
If you already have a folder named my_mod please rename either this folder or yours and amend the shortcuts
NB: This has been tested on an installation of RTW 1.5 with BI 1.6 also installed - I don't have a standalone version of RTW 1.5 so can't confirm if the expanded_ .txt file is correct for that.