When adding a sample series, the series' name will be identical to names of its samples. If you want to change the name of the sample series, you can rename the sample series. Open the sample series information sheet and click Rename.

In the pop-up window, enter the new name for your series and click Rename.

Note that only the name of the sample series will be updated in this way and not the names of the samples. These should be updated separately by editing the sample's information sheet.