[vernz]

On top:

pawn Код:

#define DIALOG_TEAMS 1

Your command:

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if (strcmp("/teams", cmdtext, true, 10) == 0) //The command
    {
        ShowPlayerDialog(playerid,1,DIALOG_STYLE_MSGBOX,"{FFFFFF}Available Teams on World War 23 TDM Server.","{00FF00}United States of America \n{FFFF00}United Arab Emirates \n{FF0000}Russian Federation \n{FFFFFF}United Asian Forces \n{008000}European Alliance \n{FF4040}North/South Poles","Okay","Okay");
        return 1;
    }
    return 0;
}

and then your dialog:

pawn Код:

public OnDialogResponse(playerid, dialogid, response, listitem, inputtext[])
{
    if(dialogid==1) // The response
    {
        if(response)
        {
            SendClientMessage(playerid,0x00FF00FF,"Good that you understand! Now proceed to battle zone and fight the others!");
            return 1;
        }
        else
        {
            SendClientMessage(playerid,0x00FF00FF,"Good that you understand! Now proceed to battle zone and fight the others!");
            return 1;
        }
    }
    return 1;
}

Hope it'll help.