Herblore training usually involves making potions. To make a potion, the player will have to gather the required ingredients, usually a herb of some sort along with a secondary ingredient, and use them on a vial of water or coconut milk.
Herblore can also be trained by cleaning grimy herbs, but that's a much slower method.
Herbs can be obtained from farming or as a monster drop. Killing ankous is one of the best methods to obtain herbs as they drop a lot of noted herbs. Ankous can be found, among others, in the Catacombs and the Stronghold Slayer Cave. Both places can be reached by using the corresponding teleport under the Slayer Teleports.
Secondary ingredients can be bought from the General Store in Edgeville.