Welcome @SaibotMagd
I’m not sure which server you are working at (the URL) but if that target server supports an OMERO connections, this is how to access your user preferences at a Galaxy server.
Create or log into your account.
This is a simple guide that will apply to most Galaxy servers → FAQ: How do I create an account on a public Galaxy instance?. The screenshots are for a different release, but maybe comparing to the new screenshots I’m including here will help to get your oriented too, no matter which release may be running?
Click into the User menu in the masthead (to the right at the top)
The preferences will list out the options available at that server.
The Manage Information section is where most of the external keys and configurations are set up but you can explore the others. Some common examples are in this guide → FAQ: How to update account preferences?
One server that supports the OMERO connection is UseGalaxy.eu.
Please let us know if this actually helps or not! Maybe share a screenshot of where you are stuck that includes the server URL at top. We can help to double check if this option is supported or not there, and maybe look into why.
And I just re-read – is this really on a local server? What does your deployment looks like? Have you tried the instructions here yet? tools-iuc/tools/idr_download/README.md at main · galaxyproject/tools-iuc · GitHub (linked at the bottom of the blog post). I wasn’t sure if you just had trouble finding it or if the config is the issue. The version of Galaxy would be helpful and please note if the Docker Galaxy or something different we can point you to the correct administration docs for locating config files. Xref → Private Galaxy Servers
Thanks! 
Yes its a local server installed from by using the Docker image: GitHub - bgruening/docker-galaxy: 🐋📊📚 Docker Images tracking the stable Galaxy releases. I’m in contact with Björn Gröning but we couldn’t find a solution yet. The credential menu just doesn’t apear in the preferences menu not for omero nor ownloud or anything else. its just empty as it is. I used every guide you posted and tried on every file. So the issue seems somewhere else.