Determine what your ticket code is for. Some codes are only valid for specific concert locations and dates. If it's a show you want to attend, note the day and time that the presale starts.
Go to Ticketmaster's website the day of the sale. Most presale codes are only available for online purchasing. It is best to get to the website at least 15 minutes before the presale starts so you are ready to get the tickets the minute they go on sale.
Type in the name of the artist in the search bar. Select the location that you have the code for. It may say that tickets aren't available yet. Make sure that you have the ticket code ready. It may be best to copy it so you can paste it directly into the box when the time comes.
Refresh your page when the time comes that the tickets are supposed to go on sale. Your computer time may not be in sync with Ticketmaster's clock, so you may need to refresh for a few minutes before they show availability.
Select the amount of tickets you'd like and choose a price range. Paste your ticket code into the section that asks for a "presale password." Click "Find Tickets" and then you'll be asked to enter a security check code, where you retype the text in a box. If tickets show up that match your criteria, select them and purchase.