So, I wanted to test giving players skin and it just didnt wanted to work.

I first tried to do like in your video but it didnt wanted to work saying that I needed a number instead of the name of the skin. so this is what I tiped and This is what shows in my console :

Zakkaroom issued server command: /armourers setSkin Zakkaroom 8
[00:08:12 ERROR]: Couldn't process command: 'armourers setSkin Zakkaroom 8'
java.lang.ArrayIndexOutOfBoundsException: 3
at riskyken.armourersWorkshop.common.command.CommandSetSkin.func_71515_b(CommandSetSkin.java:57) ~[CommandSetSkin.class:?]
at riskyken.armourersWorkshop.common.command.CommandArmourers.func_71515_b(CommandArmourers.java:88) ~[CommandArmourers.class:?]
at net.minecraft.command.CommandHandler.func_71556_a(CommandHandler.java:99) [z.class:?]
at org.bukkit.craftbukkit.v1_7_R4.command.CraftSimpleCommandMap.dispatch(CraftSimpleCommandMap.java:53) [CraftSimpleCommandMap.class:1.7.10-1614.58]
at org.bukkit.craftbukkit.v1_7_R4.CraftServer.dispatchVanillaCommand(CraftServer.java:756) [CraftServer.class:1.7.10-1614.58]
at net.minecraft.network.NetHandlerPlayServer.func_147361_d(NetHandlerPlayServer.java:1377) [nh.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147354_a(NetHandlerPlayServer.java:1107) [nh.class:?]
at net.minecraft.network.play.client.C01PacketChatMessage.func_148833_a(C01PacketChatMessage.java:38) [ir.class:?]
at net.minecraft.network.play.client.C01PacketChatMessage.func_148833_a(C01PacketChatMessage.java:53) [ir.class:?]
at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:245) [ej.class:?]
at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:181) [nc.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:1023) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:432) [lt.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:841) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:693) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_181]