client.on('guildMemberAdd', guildMember =>{
    let welcomeRole = guildMember.guild.roles.cache.find(role => role.name === 'YOU_ROLE');

    guildMember.roles.add(welcomeRole);
    guildMember.guild.channels.cache.get('YOU_CHANNEL_ID').send(`Welcome <@${guildMember.user.id}> to our server! Make sure to check out the rules channel!`)
});