To become a cryptocurrency miner you would need to put together a mathematical puzzle using soft ware for example in bitcoin the puzzle made by satoshi Nakamoto where you get bitcoin after solving the puzzle.
Bitcoin is obviously digital,and isn't physical in anyway,what miners do is,when an order is placed by a customer,its the duty of miners to confirm this transaction and move it over to another block, and they do this but solving a cryptographic puzzle,and the first miner to solve this puzzle is rewarded with
bitcoin from thin air/transaction fees
The 21mln bitcoin has already been programmed,so when a miner successfully confirms a transaction,he/she gets rewarded(they do not technically create bitcoins)
OP's comment is just weird! i don't know why he even started this topic when he is not even familiar with mining. your comment is better, i just wanted to add this.
i personally don't like calling mining a "puzzle". there is no puzzle. it is the common hash function (SHA256) that you perform multiple times until you satisfy a condition!
as for new coins, miners do technically create bitcoin! when a miner finds a new block he is awarded by newly created coins which is a fixed amount (currently 12.5
BTC) in other words they "create" a new transaction known as coinbase transaction which pays them this newly generated coins. it is not out of thin air, it is the design of bitcoin to distribute the 21 million supply in this manner.