As commissioner, you have the option to process a trade immediately, wait out the full processing time, or decline it.
The processing time is based on your setting for Time to Review Pending Trades:
Keep in mind that the commish is the only one able to deny any pending trades as we don't support vetos.
You'll be able to view any pending trades at the bottom of your league homepage in the section titled "League Activity".
On mobile, it'll look like this:
You can see when the trade will take effect and you can choose to process it now or remove it.
On web, it'll look like this:
At the bottom, you can tap into that outstanding trade and get a window that allows you to view the details of the trade.