I set up a USDC pool on uniswap today to learn about exactly this. The answer is that I had to set an initial price, which I matched to the current ETH pool price to avoid disrupting things. Then, with v3 at least, i had to set a minimum and maximum price for the token swap. The price is balanced between those values as tokens are swapped. For example, I set the maximum swap price to something ridiculous like 500USDC for 1 yieldly. If the price ever reached that, my entire position would be in USDC. After setting up the pool and paying the ridiulously high start up fee i have seen 3 transaction that werent me. the price shifted based on demand and the liquidity of the side on demand.