I've dealt with several other people in the same situation as yourself, in the past 3 months. They have all managed to make successful articles. It might sound complex at first, but it's really not so bad.
First, I recommend reading the welcome thing above; the best way to get going is to follow that - play around a little, and edit some other articles, before starting your own.
When you're ready to make the article, first, read the following docs carefully;
WP:COI,
WP:BESTCOI and
WP:BFAQ.
Following the principles of 'bestcoi', start creating the article in your own user space - e.g.
user:Chzz/help/mypage. Add references for everything - make sure they are
reliable and
verifiable sources. The webpage of the charity is a primary source, so may be challenged. For example, if you say "The organisation has 3000 employees" with a reference to their own website, that information may later be removed. If you can source a national newspaper article that mentions the fact, it should be OK. For help with how to make good refs, see my own tips in
User:Chzz/help/refs.
At the same time, get in touch with other people in the community. Go to their talk page, create a new section, and say hello. Remember to 'sign' your message, with ~~~~ at the end. Some of the others I've helped with this include;
It's also worthwhile you reading through their talk pages, to see the issues they faced with their articles.
When you've got the article into shape, ask someone to look at it. You could ask a helper in
IRC, or put a request on
WP:FEED.
Sorry if this seems like a lot of info to take in, but from experience I've found it to be the best approach. There are lots of people in the Wikipedia community who will help you in any ways we can.