Our first steps help file and our FAQ will help you a lot after registration. They explain how to customize the interface (for example the language), how to upload files and our basic licensing policy. You don't need technical skills in order to contribute here. Be bold contributing here and assume good faith for the intentions of others. This is a wiki - it is really easy.
When picking categories, try to choose a specific category ("Astronomical diagrams") over a generic one ("Illustrations"). Pro-tip: The CommonSense tool can help you find the best category for your image.
Thanks again for your uploads! More information about categorization can be found in Commons:Categories, and don't hesitate to leave a note on the help desk.
The developer team at Wikimedia is making some changes to how accounts work, as part of our on-going efforts to provide new and better tools for our users like cross-wiki notifications. These changes will mean you have the same account name everywhere. This will let us give you new features that will help you edit and discuss better, and allow more flexible user permissions for tools. One of the side-effects of this is that user accounts will now have to be unique across all 900 Wikimedia wikis. See the announcement for more information.
Unfortunately, your account clashes with another account also called Alargule. To make sure that both of you can use all Wikimedia projects in future, we have reserved the name Alargule~commonswiki that only you will have. If you like it, you don't have to do anything. If you do not like it, you can pick out a different name.
Your account will still work as before, and you will be credited for all your edits made so far, but you will have to use the new account name when you log in.