Here is a list of the account records that the user can access. Notice that the list includes an account whose type is marked Competitor. sfCRM uses this account type to mark competitor accounts.

To display your competitor accounts, click the lens icon to invoke the quick find tool.

The quick find tool appears as a popup window.

In the popup window, choose the account type field for matching.

Choose Competitor as the match value.

Click the "Go" button. Notice that the results have been chosen to appear in the main window rather than in the popup.

The list of competitor accounts appears in the main window.

If you click a particular competitor account record and then click the "Opportunities" tab at the bottom, you can see the opportunities in which that competitor is involved.

When you add a new opportunity, or edit an existing one, you will see your competitor accounts in the screen. You can then select the ones that are involved as competitors, and save the changes.

You can also find the competitors involved in a particular opportunity by clicking the opportunity record in question, and opening the accounts tab.