You can get them by obtaining clay, then using a bucket of water on the clay to make the clay into soft clay. Once you have that, you must obtain the runes that are required for the certain spell and enchant it using your player-owned houses' lectern. The minimum level for enchanting the soft clay, is level 40 construction. Once you have that certain level, you can enchant them with certain spells by using your lectern. When creating your lectern, you need at least 1 oak plank for the Oak Lectern. As you progress in construction, you can build better lecterns that require different materials.