For a Windows computer:

1. Type Control Panel into Windows search box
2. Click Network and Internet > Network Connections > Change Adapter Settings
3. Right-click on the active connection you are using and select Properties
4. Locate Internet Protocol version 4 in the window, left-click on it, and select Properties  
5. Click > Use the following DNS server addresses, and input your alternative address settings

For a Mac:

1. Open your Apple Menu and select System Preferences, then click Network
2. On the list to the left, you will need to select the network connection you are currently using (WiFi or Ethernet), then click Advanced
3. Select the DNS tab, then click the add button at the bottom of the DNS Servers list, and enter the preferred DNS Servers you wish to use
4. Click Ok to apply these changes