It's not possible to put cannabis flowers in a JUUL, as it's not designed for use with dried herbs. However, you can use your JUUL to smoke marijuana concentrates by putting liquid vaping juice with THC in a pod. If you buy a mix of e-cigarettes, it works quite well, but I recommend buying real oil cartridges as they are more effective. The juice capsules may drip a little, so they can be wasteful.
Vaping THC oil requires heating the oil and inhaling it through a vaporizing device such as a vaporizer or an e-cigarette. Many healthcare providers are concerned about the potential health risks associated with this type of THC product. Your vaping capsule will contain your e-liquid and vaporize it. You can then inhale the vapor through the mouthpiece.
It can be used for regular e-juice loaded with nicotine or for a marijuana tincture (if the device does not use pre-filled cartridges). Most vaping capsules have a maximum capacity of 2 ml, although you can find larger ones if you compare prices.