We need more information:
- Is your computer showing the ethernet cable/wireless connected?
- Does it have an IP assigned? (you can check that by running the ipconfig command from cmd)
- Can you make a successful ping from your pc to your router?
If all of the above works you should be able to the IP address 8.8.8.8, if that ping works but still can't navigate it could be a DNS issue, check your DNS configuration.
If all of the above works but you can't ping the IP address 8.8.8.8, either you have a bad default gateway configuration or your ISP is having some issue with your connection.