For charts, you can use VisualEdit. It's much easier.
For images, you have to upload them to Wikimedia Commons first, then you can added the images to the Wikipedia article. Non-copyrighted images on Wikipedia are generally taken from Wikimedia Commons.
Here is the link to Wikimedia Commons:
https://commons.wikimedia.org
Most importantly, when adding or modifying information, be sure to include a reliable source. Guidelines can be read here:
https://en.wikipedia.org/wiki/WP:RS
Edits are often reverted without reliable sources for good reason.
It is best to register on Wikipedia as it allows for the ability to edit many of the more popular and/or controversial articles (semi-protected articles can only be edited by registered users that have registered for a few days and made a few edits) and Wikipedians are more likely to trust edits made by registered users.