Bottom right corner of your Window you should see your programs currently running, Double click on the Steam Icon and once Steam opens go to Games at the top of the window and click on it and select View Games Library, Now right click on the Rome: Total War Gold Edition and go to properties. In this window select Set Launch Options. This box should be empty of text. Now Input -show_err -nm -mod:bi/ci in this window and select Ok. Now press close and then little X in the top right corner this should take you back to your desktop.
Right Click the Steam Icon and select Rome: Total War Gold Edition to launch the game when the box appears asking if you want to play Rome or BI just click on The BI version and click OK.