The following help pages assume that you are logged in and have certain access rights. Some explanations may not make any sense because you don't see the described links or setting. For several of the advanced settings it is frequently safe to just ignore them. If it turns out you do need them contact the current site administrator for help.
Once logged in you will see another menu on the left side below your name. People will see different links there depending on particular access rights. However, everyone will see the link 'Create content'. This is where the contribution of News, Job advertisements, VTC materials and notes start out if they don't yet exist.
To start new content in most other sections please see detailed description on how add book pages in Managing a Project.
Existing pages have two tabs on the top: 'view' and 'edit' (other tabs are possible too depending on the content type). Click on 'edit' if you want to change any of the text on the page.
You can also leave comments on almost every page if you would like to start discussing the subject of the page or add to it.