To bloom spices simply means to heat them in oil. Blooming deepens flavor and can help evenly distribute spices throughout a dish.
To bloom spices simply warm 1-2 tbsp of olive oil in a sauté pan over medium heat, add spices — ground or whole — and cook until spices become fragrant, about 30 seconds, stirring constantly to avoid burning.
Blooming can be built in to the cooking process — you may already be practicing this culinary technique without knowing its official name. When sweating aromatics like onions and garlic, add ground spices along with the salt. Cook another 30 seconds to a minute and the spices will bloom. Don’t worry — your nose will tell you.
If you want spices to really sing, try buying spices whole, then toasting and grinding them yourself. A coffee grinder works well for this, but buy one that is dedicated strictly for spices. Freshly toasted and ground spices that are also bloomed will guarantee plenty of pumped up flavor for your next recipe.