Head to the Road to Wrestlemania mode and select the Undertaker's storyline.
You basically have 13 weeks left til Wrestlemania and are scheduled to 1 match per week up until then. You need to work your way up to the last week and once you have done that the achievement will unlock. It really doesn't take all that long to do at all (Skipping the FMV's will also speed up the process).
It would be a good idea to check the requirements of certain matches so as to unlock bonus content which will aide you in getting other achievements later on. (For example tombstone Kane 2 times in one match).