Assuming you've already used the resource manager to put them onto the database:
1.Go into the database and the tilesets tab. increase the array size by [however many new chipsets you want] and then on that new slot, name the new chipset and use the [...] to select the new chipset. You can now use that in maps.
2. YOu can only use one chipset per map, so if you hcange chipset, the whole map changes to fit the new set. If you want a map with bits and pieces from various chipsets you're going to have to make your own custom one (either from scratch or by copy/pasting the pieces you want)
Add [resolved] to the title....