The vast majority of wallets pay the transaction fee as an extra. Automatically. So when you tell it you want to send one Monero, your transaction will actually be something like 1.0003 Monero.
Edit: I know of only two situations when this is not the case. If you tell your wallet you wish to send everything, then it will send everything it can with the transaction fee so you will get slightly less.
As an example of this, if you have one Monero in your wallet and want to send that to another wallet you control and you say to send the max, you will actually get like 0.999 Monero.
The other wallet where you have to pay attention to that is the Haveno exchange wallet as it has options for both including and excluding the fee.