First, let's start with the simple things that could go wrong:
do I need to connect it to de wan port or to one of the other 4 ports?
Connect the "LAN" or "internal" port of the core to the "WAN" port of the router. (Make sure the router is set for dynamic addressing for its WAN port so that it picks up an IP address and DNS settings from the core.)
Did you make sure that your core's WAN port got an IP address from your ISP? You may have had to unplug your cable/DSL router for 10 sec and replug it back in, then reboot the core. This will force it to pick up a new IP address. You can check what that IP address is on the core by typing:
to see all your interfaces or
for your LAN and WAN ports. I don't know which one you initially setup as your LAN or WAN ports when you installed Plutohome, so you'll have to play around a bit to find out.
By "Internet cable", do you mean the cable connected to your cable/DSL modem? I'm assuming yes. I'm also assuming that when you say
I can see the pluto admin but I dont have internet
that you are able to connect to the pluto core using a web browser on another computer. If this is all true, then it may be that the ethernet cable you are using needs to be changed. For example, if it is a "straight-through" cable, change it with a "cross-over" cable or vice versa.
I hope this helps.