Unless you've been born into, or accepted by, an Indiginous Evenki-speaking community in North Asia, you DO NOT become a 'shaman,' and even then, not without a considerable, and highly culture-specific, amount of education. You're probably conflating 'shaman' with 'medicine man,' 'ayahuasquero,' or any number of other culturally distinct roles that New Age types have thoughtlessly lumped into one icon called 'Shamanism.'
Now, if you buy into the appropriation of the term shamanism and aren't too interested in cultural literacy, I suppose you can just call yourself one. There's no 'Shaman Police' that's going to kick down your door and cart you off.
That said, why do you want to be a 'shaman?' What is it about the title that appeals to you so much? Why not just do what it is you feel called to do, and do yourself the favor of not getting bogged down in new-age BS. If you want to heal people with psychedelics, find your own path. If you want to explore the 'spirit world,' that's something else you can do yourself.
Don't steal it from others, especially if you don't have a context for what they do.
The Dalai Lama (who I think is a generally pretty respected guy on this forum) has advised Western Seekers to avoid turning to Buddhism, but rather, try to find meaning in their own native traditions, not out of some sense of separatism, but because you can do more good in your own community, speaking the language of your immediate neighbors.
Blessings
~ND