1. Navigate to Services | PPPoE server, as shown in the following screenshot:

2. Click on the Add button.

3. Check the Enable PPPoE Server checkbox:

4. Choose an interface in the Interface drop-down menu (probably WAN).
5. Set Total User Count to the maximum number of users you want to be able to use the PPPoE server at the same time.
6. In the Subnet mask drop-down box, select the CIDR corresponding to your subnet mask (for example, 24 is 255.255.255.0).
7. In Remote Address Range text field, specify the starting address of the client IP address subnet. The total range will be the starting address, plus the number specified in Total User Count.
8. In the Server Address text field, enter a currently unused IP address the PPPoE server should give to clients for use as their gateway.

9. In the Description text field, enter a brief non-parsed description.
10. In the DNS Servers text fields, enter custom DNS servers, or leave them blank to use the default DNS servers.
11. Scroll to the bottom of the page to add users. You need to specify a Name, Password, and IP Address in the appropriate text fields, and click on the Add User button each time you add a user:

12. Click on the Save button when done making changes.
13. Click on the Apply Changes button.
14. You still need to add a firewall rule to allow PPPoE traffic to pass. Navigate to Firewall | Rules.
15. Click on the PPPoE Server tab.
16. Click on one of the Add buttons to add a rule.
17. Leave the Action set to Pass.
18. Change the Proctocol to Any.
19. Enter a brief, non-parsed description in the Description text field.
20. When you are done making changes, click on the Save button.
21. Click on the Apply Changes button.