Incorrect spelling, explanation: entred is a misspelling because enter is the base verb here and to create past forms we add -ed suffix (as enter is a regular verb). Enter plus -ed is entered, so entered is the correct spelling here.

Correct spelling, explanation: this is the correct spelling as enter is the base verb here. Enter is a regular verb so to create past simple or past participle we simply add -ed ending. Therefore the correct form here is entered, not entred. Enter + -ed is entered.

Definition of entered:
verb, past simple and past participle form of enter; to go/come inside or to put sth into
I entered the shop and realized I had forgotten my wallet.
I have never entered such a filthy car! You should clean it.