If you have the yellow triangle then you do not have internet access. I guess you have network access but not Internet access. What kind of internet access do you have, Fibre, ADSL, Dialup? Check the internet access is live from the router if using ADSL or Fibre. Are the correct LEDs lit. Check the cables are connected correctly and fully inserted. Switch everything off at the mains and leave it for a few minutes. Switch on the modem then the router then the computers and see if it then connects.
Still having a problem please give us as much detail of the set up as possible.
Look in Network and Sharing Centre and see where the disconnect lies.