AWS EC2 default password

I'm following this tutorial to host a website with an apache server. The thing is that the last step tells my to do

service apache2 reload

But it asks me for a password. I don't remember inserting a password for this VM, just the .pem I used to log in.

Is there a default password? Or how can I solve this? Sorry if this is basic, but the most complex thing I've done with servers is with wamp and xamp

Thanks!