File core.clj is not under a source root error in intellij

I am using IntelliJ IDEA in a Clojure project, I just started but I get the message "File core.clj is not under a source root", the project has 2 folders: .idea and src, inside src I got the core.clj file in which showing the structure of the project. This is the photo containing the structure of the project.

I have no source root, I just created the core.clj and the deps.edn file and the Deps_project.iml file, nothing else, how can I solve this? Do I need to write another file?

You need just two files for your project:

In file deps.edn

{:paths ["src"]
 :deps  {org.clojure/spec.alpha {:mvn/version "0.3.218"}}}

In file src/spec_tutorial/core.clj

(ns spec-tutorial.core
  (:require [clojure.spec.alpha :as s]))

Note there is a correspondence between the Clojure namespace and the source file path, but beware that hyphens - in namespaces are translated to underscores _ in path names.

Your directory tree should look like so:

./deps.edn
./src/spec_tutorial/core.clj

where the ./ prefix is unix-style shorthand for the project directory.

So, the ./src part is determined by the :paths line in deps.edn. The spec_tutorial/core.clj part is from the namespace spec-tutorial/core, and the .clj suffix is the "file-type".

Also, note that hyphens in the namespace become underscores in the file/directory names.

Another observation: Do not include :test-paths in the file core.clj as seen in your screenshot.