You can call yourself whatever you like these days, but if you want to become an actual functioning witch, this will take some work. You may already be what some call a “natural witch”, meaning you possess traits and abilities that correspond with what some would call paranormal or psychic abilities. Probably the first step to becoming a witch, if this is your situation, is to accept that these abilities are natural for you.
Indeed, they are a gift from our Creator, but both we and the Creator are totally natural be-ings. Awareness that you were made just fine, and that there is nothing really bizarre, messed up, or wrong, or even better value-wise about you is what makes a witch distinct from someone just bumbling along. The conscious awareness that like any other ability, it needs to be respected and channeled into a productive pursuit or even occupation, is what marks a witch.
So then the next step is to start studying. You’ll be studying all your life. If you can find a mentor or teacher to give you some guidance, this is best. If not, read all that you can and practice on your own.
Once you start this in earnest, you are a witch, at least in most places English is spoken. Be aware that different cultures have different meanings for and implications that come with the term “witch”. There may be some translation issues even with another English speaker if the term “witch” means something other than a conscious utilization of both seen and unseen aspects of Nature to manifest one’s will, in their culture. In some cultures it means specifically someone who uses their spiritual power or abilities to harm people.