Hi and welcome to GT Planet!
As Greycap said, this is the most commonly asked question on this forum (with the second most common probably being, "how do I win the GTWC now that I can enter it?"). It is considered good manners to search the forums (seach box is in the upper right corner) before asking; there is a lot of information here and this topic in particular has been discussed many times and in great detail.
But to recap: doublecheck all your trophies because it is very very easy to mistake a bronze for a gold. Also, make sure you did the championship series (Tuning Car Grand Prix, World Classic Car Series and World Compact Car Race) as championship series and not as individual races. If you go to for instance the Tuning Car Grand Prix the first icon, the shield with the GT logo and checkered flags, should also have a gold trophy under it. If not, simply click on it to enter it as a series.
A Beginners Event is a race located in the Beginner's Hall and similarly for Professional events and halls. So no, events and halls aren't the same thing; a hall is a sort of container for events.