In the Apple Menu (top left), go down to Control Panels then TCP/IP. Ignore this window for now. Go to File and Configurations.
There will be a set called Default. Highlight this with the mouse and select Duplicate. Name the set with your isp name.
Click on Make Active and the following window will appear. Insert the relevant name server addresses as below:
As this is a modem connection, we need to select Connect Via: PPP (for a network connection such as we use in this office, select Ethernet).
Click the box at the top left to close the window and select Save when prompted.
Back to the Apple Menu. Go to Control Panels and select PPP. Again, ignore the window that appears and go to File and Configurations.
Once again, there will be a Default set. Highlight this and select Duplicate. Name this set with your isp name.
Click on Make Active and the following window will appear.
Enter the correct username, password and phone number as supplied to you by your isp:
Click on Options and make sure the boxes are identical to the ones below.