Adding Descriptive Text To Images

I’m getting used to inserting images into my blog, But I have a problem and would appreciate some advice.

Let’s say I have a image located at https://www.mydomain.com/images/Eiffel Tower.gif. Using the insert/edit image icon in wp visual screen there is no difficulty in inserting the above image.

Here’s my problem. What if I want to place a descriptive text below the image e.g. Eiffel Tower how do I do that. Do I have to do it manually and if so how? Or can I get WP to do the task automatically?

Many thanks for any assistance offered