Setting up the plugin is relatively easy. A working Spigot server or variant of Spigot like PaperMC is required.
1. Download RealisticSeasons from the spigot page.2. Download ProtocolLib here: https://www.spigotmc.org/resources/protocollib.1997/3. Put both downloaded jars into the plugins folder of your server.
4. Restart your server
5. Go to the world you want seasons in and type /rs set spring. This will set the season in your world to spring and it will also automatically activate the temperature and calendar system. The season cycle starts too.
6. Check out the configuration section of this wiki if you want the plugin to perfectly fit your server. This is not necessary, the plugin will function without changing anything.