insert
in-sert
verb
To put or place something into something else, often carefully or precisely.
"Please insert the key into the lock."
noun
An item, such as a leaflet or page, placed inside a larger publication.
"The newspaper included a promotional insert."
Thesaurus
Synonyms: introduce, infix, enter, cut-in, inset, sneak in, slip in, stick in, tuck, inclose, put in, enclose