The instrument field is an auto-complete field. So if you start typing "Xevo TQ" in this field you should see a drop-down list of matching instruments. "Xevo TQ-S (Waters)" should be one of the options in the list. Select the matching option and it will be added to the instrument field. You can also type "Waters" to see a list of all recognized Waters instruments. Let me know if you don't see your instrument or are otherwise having a problem seeing the drop-down list.
This list is backed by the standardized controlled vocabulary maintained by the HUPO Proteomics Standards Initiative (http://www.psidev.info
/), and submissions to ProteomeXchange require that selected instruments match one of the supported terms in the PSI vocabulary.