Update README.md

Author: ocots

README.md

@@ -47,4 +47,4 @@ You can find first good issues (if any 🙂) [here][first-good-issue-url]. You m
 If you want to ask a question, feel free to start a discussion [here](https://github.com/orgs/control-toolbox/discussions). This forum is for general discussion about this repository and the [control-toolbox organization](https://github.com/control-toolbox).
 
 >[!NOTE]
-> If you want to add an application or a package to the control-toolbox ecosystem, please follow this [set up tutorial](https://github.com/control-toolbox/CTApp.jl/discussions/9).
+> If you want to add an application or a package to the control-toolbox ecosystem, please follow this [set up tutorial](https://github.com/orgs/control-toolbox/discussions/65).