Introduction to Editing
MusicBrainz is a collaborative database: you can (and should!) make edits to correct errors or add new data. Everything in the database is open to editing: names, relationships, dates... anything you can think of. By doing this you enter entering edits into the system, that in most cases will have to be voted on.
In the past some new data was automatically imported, but all new data that is being entered into the database nowadays is added by MusicBrainz users, like you!
In order to maintain a consistent level of quality in the database, editors should familiarize themselves with the MusicBrainz style guidelines. You are not necessarily expected to know all of these guidelines from the beginning, but your changes will be judged against these guidelines when other users vote on your edits.
To edit the database, you will need to have a MusicBrainz account and be logged in. When logged in, you'll see a new set of links in almost every page that allow you to edit the information.The edit links will take you to pages where you can edit or add information for that entity. On the edit pages you will find further instructions and links to the guidelines that will provide a guidance for this particular type of edit. Please read and follow these guides - they are important in order for the entire database to be reasonably consistent. If the edit page has more than one field that can be edited, but not all fields need to be changed, just leave the correct fields like they were. Make sure you enter an useful edit note if at all possible! You can find some tips for that here.
Once you finish editing and click submit on the edit/add page, you will be taken back to the page that you entered it from (or, for some additions, to the page you just added). An edit will be entered into the database: if you click on the Editing History link in the sidebar you will be taken to a page where you can see all the edits ever entered for this entity. For some edits, this is all that is needed - they are entered automatically. An example of this is a change in capitalization in a title. Most edits, though, need to enter a voting period before they are accepted. If you can also see an Open Edits link over the Editing History one, check it before editing! Maybe somebody has already made the change, and it is waiting for votes to be applied.
If you realise you have made a mistake, and your edit is still open, you can cancel it from the edit page, or from your My Open Edits list (in the My Data menu). Just click on the "Cancel edit" button. This is much better and less time-consuming than creating a new edit that corrects the bad one, and ensures the mistake goes away soon instead of having to wait for votes to be corrected. If the wrong edit is no longer open, you will have to enter a new edit that corrects the mistake.