I would advise you not to be using Fentanyl if you're not already involved with it. In my day, Heroin was the Opioid of choice. I had stopped using Opioids from the street right around the time that Fentanyl came into serious play in North America. I grew up revering figures like William Burroughs, Samuel Taylor Coleridge, Thomas de Quincey etc. Intellectual figures (like myself of course) who used Opioids and led full, interesting lives. They had friends, families... they made it seem like this awesome drug could have a place in our "day to day" lives.
See, even this was essentially an illusion. People can use Heroin consistently, compulsively for long periods of time under certain circumstances. William Burroughs had money, as did the English guys. That makes things a lot different. I was an English/History teacher. I did my job, passed my assessments and generally enjoyed my time in that profession. It was never going to last though. I did it for years. I would fuck up, get back up, start over, but I was always on the trajectory of hitting the the ground, it was just a matter of when.
Fentanyl takes this phenomenon and turns it up to its maximum extent. Fentanyl consumes every person that uses it. A "functional" Fentanyl user is someone who can manage their addiction for several months while working full time. They all eventually fuck up. When they fuck up, they find that there is really no effective treatment for folks with their kind of dependencies. We only have the treatments that were once effective for Heroin users.
It's not something that is easy to get out of once you've started. I've withdrawn from Methadone and Heroin, both multiple times. I know how hard that was; how unlikely I was to succeed. If you're not doing it already, find a different drug. If you hate your life, find a different drug with which to anesthitize yourself. You can figure it out later, but don't use Fentanyl.
If you do choose to use them, they can be taken orally or intranasally. Oral administration is going to be significantly weaker.