Start unified sniffing and select your interface
scan for hosts
Under plugins - use the plugin to isolate the IP of the gateway
in the host tab, assign the gateway ip to target 1
leaving target 2 blank will auto assign all ALREADY scanned hosts to be poisoned (not recommended for wifi - cards simply aren't fast enough to deal with more than a few hosts at a time) - or assign specific hosts for poisoning
select the arp poisoning attack and enable sniffing of remote connections
go to plugins and then activate the auto add host plugin by double clicking
hope this helps.