Anyone can edit Wikipedia, even without creating an account. All edits are linked to the user who made them.
Editing as a registered user can therefore increase your privacy, because your computer’s IP address will not be visible to others in the edit record.
Creating an account gives you access to additional functions beyond basic editing, such as: having your own user page with a sandbox for trying out edits, and the ability to track your contributions and apply custom preferences when viewing and editing Wikipedia.
To create an account, you only need to provide a username and password. An email address is not required.
The instructions for the 1Lib1ref event is the best place to go for a quick overview of how to do this. Read the “Adding references” section on this page: The Wikipedia Library/1Lib1Ref/Help
Wikipedia guidelines state that “articles should be based on reliable, published sources, making sure that all majority and significant minority views that have appeared in those sources are covered.” Even stated so clearly, this is a complex topic!
For just getting started, focus on the “reliable, published” aspect, and consider applying these guidelines, quoted from the Reliable Sources section in Wikipedia:Verifiability:
Wikipedia Content Guidelines Pages provide comprehensive and in-depth guidance about evaluating sources in the context of Wiki editing:
“Wikipedia favors sources that are Open Access, but it doesn't require them”, as the 1Lib1Ref citations project points out in their Tips for Sources.
Open access sources increase verifiability – they make it easier for other readers to assess whether information is backed by reliable sources. Referencing freely-available online sources allows more members of the public to find and access research materials.
Many arts resources exist in print form, however, such as books and magazines that may not be instantly accessible via the web, but are still invaluable resources for arts research, containing information that does not exist elsewhere. These are also verifiable sources!
Wikipedia:Reliable sources/Cost
For software-specific questions such as details about using the Visual Editor and understanding wikitext markup, one of the best places to go is of course…Wikipedia itself!
Wikipedia:FAQ/Editing answers the most common editing questions. Check this out if you're stumped!