You don't have any dial pausing options with a landline, so you'll just have to dial the number as you normally would.
 For many menu systems, you can start entering the extension as soon as the call is picked up. Try entering your extension now to see if it dials.
 If you can't immediately dial the extension, listen to the menu options. You may have to pick an option to be allowed to enter an extension.
 Some phones that have a speed dial function will also have a Pause key that you can use when programming a speed dial number. The existence and location of this button varies from model to model. If you can add pauses, enter the base number, two pauses, and then the extension number. Save the entire thing to your speed dial entry. If the number you are calling supports entering the extension immediately, you'll be able to use this speed dial entry to call the extension directly.
 If the extension is a four-digit number, you may be able to dial it directly by replacing the last four digits of the base number with it. For example, if the company number is 1-800-555-2222, and the extension is 1234, try dialing 1-800-555-1234.
Dial the number as you normally would.
Try entering the extension as soon as the line picks up.
Listen to the menu options if your extension doesn't work.
Add a pause and the extension to your speed dial (if possible).
Try replacing the last digits of the base number with the extension.
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