Prickly Pal Cactus Seeds can be made in the Processor from Prickly Pal Cactus or obtained as loot or pet harvest from Parrokis.
One Prickly Pal Cactus can be processed into 2 Prickly Pal Cactus Seeds each without requiring any crafting recipe. These Seeds can then be planted on tilled land or on Dirt, Grass or Mud to grow into more Prickly Pal Cactuses.
Grown Prickly Pal Cactuses can be used in the Cooking Station to cook a wide range of Food. Food can be consumed by player characters to be granted many different buffs (positive effects) and also fed to Pets so that they can then be harvested from.
Seeds cannot be eaten by player characters or Pets directly.
You can grow Crops like Prickly Pal Cactus from Prickly Pal Cactus Seeds on tilled blocks of Dirt, Grass or Mud or on (non-tilled) Dirt, Grass or Mud. First place such natural blocks over a body of Water or Mineral Water, or alternatively place these liquids directly adjacent to each such block (like directly below for example, or at least corner to corner).
This can even be done underground in complete darkness and/or in a building, but not at too high altitudes, not in too cold nor too hot Biomes/layers, and not too close to Swamplands or pools of Bog Water. In these cases, Seeds will stay "fallow" and won't grow (they can be picked up again though).
Next place the Seeds on the suitable blocks next to the liquid (just like you'd place any block). If you want to use tilled land, you need to first craft a Plow and use it on the solid blocks to till them. You can, but you do not need to fertilize Seeds in order to make your Crops grow faster.
Wait a bit until the Crops are ripe to receive the best harvest. Prickly Pal Cactus needs 60 minutes (real-life-time) to grow from seeds into ripe plants, even if you're offline.
Crops can be harvested by being "pulled" with the gauntlet and left mouse button (by default) just like any other type of block, item, plant or liquid. If Prickly Pal Cactuses stay "ripe" for 20 RL hours, they will turn into "grown" Crops. The harvest will become a little less then, but Crops won't wither.
Please refer to the article Farming if you want to learn more about growing Crops.