There are two main things we look for to determine whether or not a BTC deposit will be instant:
RBF (Replace-By-Fee) must be turned off on the wallet you are sending your BTC from
Your BTC must be sent with an adequate fee
Typically RBF is already off if you are sending your BTC from a large exchange such as Binance, Kraken, Coinbase, etc. If you are depositing from a wallet there may be an option to disable RBF - for example these instructions you can find here for Electrum and Bitcoin Core wallets. You will have to explore your preferred wallet/exchange provider or speak to their support to find out if they can help with this.
If the fee is too low, your deposit will not qualify to become an instant deposit. Please explore your preferred wallet/exchange to see if you can customize the fee your deposit is being sent with - the higher the fee the more likely the deposit will be instant (assuming RBF is disabled).
Please note: there are secondary factors as well that we cannot discuss. Sending a BTC deposit with Replace-By-Fee disabled and an adequate fee will never guarantee an instant deposit, but it will increase your chances.