Many institutions and organisations have created repositories for displaying, storing and disseminating digital content produced of the staff and sometimes learners who work and study there. Repositories can contain a wide variety of materials including:
What repository content has in common is that it has all been produced for use elsewhere: for publication in a journal, presentation at a conference, to assess a learner's progress etc.
For the most part, you will own the copyright to your work, but there may be a few exceptions
If you submit an article for publication in a scholarly journal, the chances are tat as part of the agreement to publish your article, you have to transfer copyright to the publisher. Having done that, you cannot upload your article to a repository. You can provide a link to it, but if you make the article available, you are breaching copyright and at the every least will be asked to remove it.
Some journals allow you to maintain copyright of your work and share and deposit them to a repository without issue. Many journals only allow specific versions of the article to be submitted. These are:
You can find the details of what version (if any) you can submit on the publisher agreement on the journal website or through SHERPA/RoMEO. Contact the library for more information
If you work at institution A but are studying or have studied at institution B and have written or are writing a these or dissertation, then it should be uploaded to the repository of institution B only. You did the work involved at institution B so it's theirs to upload. For the repository of institution A, you can provide a title, abstract and link to the work on institution B's repository, but not the work itself.
For works produced for conferences such as presentations, poster presentations and conference papers, you typically retain copyright to your work unless stated otherwise. Generally these can be uploaded to a repository without any problems. If you have signed any agreement or contract with the conference organisers, this may detail the copyright ownership of your work. You should consider the copyright policies of conferences you wish to present at in the future.