There are several places to get altimetry data. Depending on the mission you should go to a different place. You can check the section “Data Access” and see different places to get the data.
There are different types of data. You could get data with waveforms and then you run your code with the retracker you want to get the retracked sample and translated into range and after that into sea surface height. You could also get data with the retracking process performed so you would find there the different values of range or sea surface height.