1. Using SpawnProtection
You can enable this from the LEET app (under 'SETTINGS' or 'CONFIGURE'). This way does not cost any credits but might not work.
Purchase/enable the LandProtection plugin from the LEET app and create an 'area' you don't want there to be PvP (in this case it's the spawn). Once you've created an 'area' then use /area toggle <name> pvp off to disable PvP in that area.