To get lapis lazuli in Minecraft, you will have to find lapis lazuli ores. The blocks of this mineral have small navy blue specks (not to be confused with the diamond, which color is a lighter blue). This is a scarce mineral. In creative mode, it is available in your inventory from the beginning, but in survival mode, it is more complicated.
First, you must get a stone pickaxe or a tool of superior quality. To do this, you will first have to collect wood and create a crafting table. Then, with more wood, you will have to create a wooden pickaxe (3 pieces of wood at the top and two sticks in the two remaining central holes) to efficiently dig on the ground and find a stone. Once you have it, you must combine stone and wood on the crafting table to create your pickaxe. The stone pickaxe is the minimum requirement to obtain lapis lazuli, if you have a superior quality pickaxe, you will be able to find what you are looking for faster.
Your next step is to start digging. The blocks of this material are found between level 32 and below, although their maximum concentration is in layer 19. Look in places that have water nearby. Each mined block will give you from 4 to 8 lapis lazuli stones without the use of an oven.
If you have a silk enchanted pickaxe, you can extract the whole block or ore. As usual in these cases, that block can be melted in an oven to obtain the final lapis lazuli.
The uses you can give to lapis lazuli are quite limited and do not go beyond dyeing blue wool or being used as a decorative element in the constructions you make. Still, many users are interested in finding it for their own purposes, and this guide can be very helpful.