。
I met someone called Kimura at the party.
Literal
Kimura-san [called-という] person [to-に] party [at-で] met [emphatic-よ].
~という人 ('a person called X') is a standard frame for introducing someone the listener may not yet know. The という ties the name to the noun 人 — literally 'a person who is called Kimura.' Compared with the bare 木村さん, ~という人 signals that the speaker isn't sure the listener already knows the person being introduced.