Hi @lubna_najeh,
If you build a Server App this is a way to provide a user access to run a workspace without giving them access to anything else on the FME Server interface.
The Server App does not use the Guest account but instead it generates an API Token for use specifically with that App and this is how access to run the workspace is granted. Therefore to provide the user workspace to the Output you will need to register it to run under either the Data Download or Data Streaming Service, as you have set up in this post (https://knowledge.safe.com/questions/111132/fme-server-fails-to-display-the-fme-app-result-url.html).
If you would like to give a User access to certain resources you can
a) Build a workspace that fetches the data from that resource and create a Server App to run this under the Data Download Service so that the user receives this resource.
b) Create a user account with the permissions to access that Resource location and give these credentials out to that user.
Thank you @hollyatsafe , It works with me now :)
Best,
Lubna