To add samples to an existing series, open the information sheet of the sample series to which you want to add the samples. Click the Series button to add additional samples to the series.

In the pop-up window, find and select the samples you want to add from the Inventory Browser. Multiple samples can be selected from a storage layer by marking the checkboxes from the list (note: boxes need to be toggled to List View first).  Once the samples have been selected, click Choose these samples.

The selected samples will be added to the series, and the series' size will automatically be updated.