Make sure that:
In order to use Holograms, you will need to have the option holograms.enabled set to true in the config.yml.
Once you've done that, you go to the section leaderboards in the config.yml. You will have to enable all stats you want to use their. By default is only the ELO stat enabled.
Now reload the plugin using /sw reload
Now go to your the folder plugins>Skywars and open the holograms.yml file. In this file are all formats stored.
In the file, you see a section for all stat types (elo, wins, kills etc.). It's not possible to add your own stat, but it is possible to create your own format. Formats are the subsections you see in the stat type sections. For elo is it by default leaders and topplayer.
You can add, change, remove formats if you want. Then reload the plugin again.
Now you can create your holograms using the ingame command: /sw hologram [stat] [format].
As you read in the previous step, is the [stat] variable the stat type. So this could be either wins, kills, deaths, elo, losses or xp.
The [format] variable are formats of those stat types, as you also read in the previous step.
An example command could be: /sw hologram elo leaders whereof 'elo' is the stat and 'leaders' the format. A holograms will now be placed at your eye location.