First of all I think you are a little pusillanimous individual for crying about your sister.. but I will help anyways.
First open command prompt

Find default gateway

Type this in your URL bar in your browser

Type it without /admin
A box like this should show up

You need to find out the password try it blank try it with admin admin.
If that doesn't work you need to find the default username and password online, look it up
You are pretty much on your own from here on out, try to find a security box or something like that you need to look around.