Friend, I am not a walking tutorial.  The spot pair is here https://www.bybit.com/en-US/trade/spot/DASH/USDT  Deposits are done here https://www.bybit.com/fiat/deposit use the search bar to type in Dash and select it for depositing coins, you can also deposit USDT directly or other coins, note that you will need USDT for the actual trading not Dash.  Please NFA and DYOR.  All the best.