Dual sim on single simm Phone topic

Hey.. Ive manged to install the Brazilian dual Sim firmware..and i cant seem to chance it
iv got falcon_retgb_user_4.3_14.10.0Q3.X-76-LGG-8_54_release-keys-cid7-Retail_GB
but it doesnt seem to do anything
im new to all this
any advice would be great

Thanks