I'll try and answer this, however I sometimes lack the ability to put things in simple terms.
Firstly with regard to
www.e164.org, this is a DNS zone, similar to going to a website and typing in
www.e164.org rather then the IP address. In this context, we type in a phone number and get a SIP URI back, eg.
+18005558355 gets turned into
18005558355@tf.voipmich.com
Now before e164.org will let you add your number, and your SIP address you need to verify it, this means having the system call your PSTN number and will read out a PIN, you then enter that PIN into the website.
If you don't run your own SIP proxy, you will need an account with one, such as
www.voxalot.com, then you point your PSTN number at your voxalot account.