Don't just describe the image, fill the alt text with SEO terms.   No wasted words, consider the alt text to be for the eyes of the search engines only.

In general text, you can Insert/Edit image and set the Image Description.  Picture blocks have descriptions in the advanced tab.

Go to each page and edit its page properties. Set the "Page URL Alias" to be something with the core SEO term in it.

• Do use hyphens. Search engines are not humans. You might think the Freemonthyopnotherapist is "Fremont hypnotherapist", but to them it could also be "Free hyp the rapist".  Make it easy for the search engines - break up the words and take away the surprises.