AUTOSET will typically handle this for you however, if you wish to do it manually or need a specific resolution here’s how.
The TAS 455 has a Magnify button that will adjust the waveform by a factor of ten. The MAG button is used here however, this will most likely vary scope to scope. Using any magnification will also result in needing to readjust the signal using the controls described in “Displaying Repetitive Signals.” Also, to the right is a helpful cheat sheet for menu access for the TAS 455. If you have a different scope see if you can find a menu map from the manufacturer, the maps are very helpful.