We have an entire tag dedicated to this! Please read it and it will hopefully give you some good ideas on handling the situation.
My short advice for you is this:
If you are dependent on your parents still, in spite of being legally an adult, it may be better if you postpone your locks a bit longer. Parents won’t always like the changes we make to our appearance, but if you make them when you are independent, you’ll have less reason to argue.
If you will be moving out and getting to be on your own, or perhaps are going off to university for a while, maybe that would be a good time to explore the new hair.
Read our blog thoroughly. Work to explain that, “Yes, you actually do wash locked hair regularly,” and “Yes, you actually can keep them looking tidy and find employment with locked hair,” and, “No, not only [insert stereotype here] get locked hair, and people from every walk of life choose to lock their hair for a myriad of reasons.”
Try to explain things like that to them.
In the end, as long as you are dependent on them, you’ll have to respect their wishes. Read up on our parents tag, arm yourself with knowledge, share that knowledge with your parents, and make the best possible decision from there, alright?
Have a lovely day!