Bob has already explained where your duty lies. Note that there’s only a couple of weeks from the official announcement to the close of nominations (18th March to 3rd April) and the nominations have to be delivered by hand to the Returning Officer at MSDC in Haywards Heath.
Click the image for the single page flyer. But, if you really want to know all about local councils, then click here (eleven page PDF).
If you plan a nomination, or a proxy vote, then you need to read the Notice of Election sooner rather than later!