If in can ask an other question, lets say that we have the scenario of multiple IP's from my ISP "Pool" and i want to signed them in different host systems.
I suppose you have "5 usable public IP" addresses from the ISP, e.g. 192.0.2.42-46 and the mikrotik is .42, but you want to send .43 to an internal host for ALL ports (so the host can run anything it wants - it essentially has a public IP on it)
You do the same thing as the first rule you already did - but with a few changes-
add dst address = 192.0.2.43 (or whichever of the public IPs you want to map to the internal host)
remove protocol, dst port, and in interface
On the action page, change the "to address" to be whichever internal IP you want and remove the to ports.
For each additional public IP you map through the firewall, copy this second rule.
This method is 1:1 nat - where you assign an IP address entirely to one internal host.
If you specify certain ports in the General tab, and different IP/ports in the Action tab, then you can use 1 IP address but send the different services to different hosts. (so one public IP can appear to be your mail server, dns server, and web server, but behind the firewall, they are 3 different computers)
Finally, you need to configure Interfaces > Ethernet - edit the ether1 gateway interface, and make sure arp = proxy-arp, and then create a static route in IP > Routes
destination = 192.0.2.40/29 gateway=Ether2 Lan-Master (or whatever interface is the LAN)
This last two steps makes sure that the Mikrotik will answer ARP requests for all of the public IP addresses, and not just its own.
If you have filter rules in your firewall, then make sure that they allow connections to your shiny new servers on the ports you need, but not on anything else.