[Skimmer]

You need a command with parameters include and I'd recommend to use Zeex's zcmd.inc, because it's a simple include for beginners with these commands.

https://sampforum.blast.hk/showthread.php?tid=91354

Don't forgot to add sscanf to your script, because this script makes your script easier.
(Just copy the stock code and paste it to your script)

https://sampwiki.blast.hk/wiki/Sscanf

Open your script and include the y_commands before you start at scripting.

pawn Код:

#include <zcmd>

Then find an empty place, that you want write your command there.
(IMPORTANT! Don't write your command in a callback)

pawn Код:

CMD:skin(playerid, params[]) // Creating the /skin command.
{
    new skinid;
    // If you want make this command only available for Rcon Admins, then remove // characters below this.
    //if(!IsPlayerAdmin(playerid)) return SendClientMessage(playerid, 0xFF0000FF, "You aren't allowed to use this command.");
    if(sscanf(params, "d", skinid)) // d or i = integer, s = string and f = float! As you know skinid is an integer and i defined 'd'
        return SendClientMessage(playerid, 0xFF0000FF, "USAGE: /skin (skinid)"); // Player has used the command without params, then we send him a message.

    // Now the variable 'skinid' contains the value that player has gave as params.
    // Example /skin 294 and the variable contains now the value '294'

    if(skinid > 299 || skinid < 0) // There are only from 0 - 299 skin id's and it should send a warning message
        return SendClientMessage(playerid, 0xFF0000FF, "Invalid Skin ID!");
        
    // Now everything seems okay and we change his skin!
    SetPlayerSkin(playerid, skinid); // As you know the 'skinid' contains the value of player's given params.
    return 1; // Of course we need return a value.
}