A seed phrase is a series of words used to create both the public and private keys of your wallet. It should never be shared or entered into a website or posted online. The only reason you would want to enter it into a piece of software is to restore a wallet to it.
If you give someone your seed phrase you are giving them your wallet and complete control of any assets tied to it. There is no way to revoke access to someone you have given your seed phrase to, and no way to change your seed phrase.
NEVER SHARE YOUR SEED PHRASE WITH A WEBSITE OR PERSON UNLESS YOU KNOW THEM PERSONALLY AND TRUST THEM COMPLETELY.
If you have given your seed phrase to someone and you no longer want them to have access to the wallet you will need to create a new wallet and transfer your crypto and assets out of the one you gave away.