Okay, you entered it in the parameters declaration area but didn't actually make it a parameter (criteria). Try this
PARAMETERS [Enter Name] Text ( 255 );
SELECT PERSON.ID_PERSON AS PERSON_ID_PERSON, PERSON.NAME, PERSON.SEX, items.ID_ITEMS, items.ID_PERSON AS items_ID_PERSON, items.[ITEMS BOUGHT]
FROM PERSON INNER JOIN items ON PERSON.ID_PERSON = items.ID_PERSON
WHERE (((PERSON.NAME)=[Enter Name]));