How Do I Delete a Wireless Password for Apple Mac?

Open 'Finder.' In your Finder window, navigate to the 'Applications' folder and then into the 'Utilities Folder.' After you've opened the Utilities Folder, find 'Keychain Access.'
Double-click on 'Keychain Access.' When the program opens, you will see a window divided into three panes. Before proceeding, click 'Login' in the Keychains pane at the top left. Immediately below, in the 'Category' pane, click 'All Items.'
Scroll through the list of saved passwords on the right. If you have a large number of passwords, you can sort them according to name or kind to make the list easier to navigate. To resort the list, click on 'Name' to sort alphabetically or 'Kind' to sort by type of password. When you've located the name of the wireless network password you wish to delete, click on that name once to highlight that keychain entry.
Press the 'Delete' key on your keyboard. A dialog will pop up asking you to confirm that you want to delete the keychain. Make sure you have selected the correct keychain entry, because you cannot recover deleted keychain password entries. When you have confirmed the proper entry, click 'Delete' to remove the wireless password you selected.
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How to Remove Unwanted Start

Click on the 'Apple' menu and select 'System Preferences.'
Click on “Accounts” to open the Accounts preferences pane. Select “Login Items.”
Click on the lock icon in the lower-left corner and enter your user administrator password.
Highlight the application you wish to remove from your startup items and click the '-' button under the startup application list to remove the item. The next time you restart your Mac, the removed item will no longer be in the system startup queue.
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