To view any layer as a WMS you will need to create a configuration in your Dashboard. You can do this with the Collection ID of your Pleaides data and an evalscript (e.g. True Color image). Then you will be able to view this in EO Browser. For more information, you can consult the documentation here.
To answer your second question, you can use Process API like you would with any other data collection. Alternatively, for 3rd Party Data Import, you can download the original product either from the Dashboard or programatically. More information about this can be found here.