Linda, when you check "View New Posts" or "View New Posts" any topic that has a red icon to the left of the title has a new entry since you last read the topic. If you hit your browser's REFRESH button, you can easily check for new entries since you opened the forum this time, or make sure you have read all the new stuff.
When you open a topic, if there is a red icon to the left of the authors screen name (upper left of the text box under the title of the topic)
it is a topic you haven't read yet, or at least is on a page you haven't completely read.
You can also choose to have the posts appear in either ascending or descending order by date in the User Control Panel.
Just set it up according to your preferences!