The site does not make a clear declaration but my understanding is that this is named point P. The core of all bitcoin calculations. Is this correct?
This point (the Generator Point) is more commonly referred to as G.
So, please, where can I find the arithmetic steps to transform a private key into a public address?
What you're looking for is: elliptic curve point addition over a finite field
The private key is a scalar value indicating how many times you must add the Generator Point (G) to get the public key point.
For example,
If the private key (represented in base 10) is: 7
Then the step to generate the public key is: G + G + G + G + G + G + G
This looks like a pretty good explanation about how elliptic curve point addition is done with finite fields:
https://www.rareskills.io/post/elliptic-curves-finite-fields