Note that if only four nodes are Lost Ark Gold litup, engraving won't be able to have any effect. If you are able to accumulate enough bonuses to illuminate at least 15 more nodes, the excess has no effect.
There's also a third kind of engraving. These are all downside, and might reduce the speed of your attack as well as damage, defense or even your movement speed. I'll be back on these jerks later on.
When you have completed the West Luterra part from Lost Ark, two slots on your profile's gear tab open under the slot to hold weapons. Each slot can be equipped with an engravings within them. You'll see both equippable classes engravings and fight (or "combat") engravings within their submenu that can be opened by pressing alt-I. At first , you won't have anything to equip since you'll need to learn how to make them through reading recipes.
The tutorial quest that is relevant will Lost ark gold buy provide you with some as well as a plethora of the green satchels that contain engraving recipes as rewards from sidequests East Luterra, and a handful afterward on Tortoyk, Annika, and Arthetine. Engraving Recipe Pouches provide random recipes, while engraving Recipe Selection Pouches let you choose what they're made of and are best reserved for the moment you've decided on the build you want to make. There are distinct pouches for class and battle recipes, too. (Sometimes the latter may be called 'combat' recipes, but they're the same as the battle recipe.)