The occupation system in Forsaken World (aka jobs, professions) allows you to specialize in numerous crafting professions that will let you create everything from potions to armor. You can view the occupation menu by hitting the "o" key. This system is automatically unlocked for your character during the starting quest line in Freedom Harbor.
In order to learn professions, you first need to acquire job points. To gain job points, simply complete quests in the main quest line (these quests are color coded yellow in your quest log). At certain milestones, you'll be rewarded with an additional job point. To spend a job point, you must visit the trainer for the occupation you want to learn, and purchase the occupation there.
Certain jobs require you to reach a certain level before you can learn them. Additionally, you will not be able to learn all occupations on one character - so choose wisely.
To use an occupation, click on which one you want to craft with in the occupation menu. This will list all of the recipes you've learned, as well as the requirements to create each item. Recipes can be gained from quests, killing monsters, and events. Right click a recipe to learn it.