。
She kissed the crying boy and soothed him.
Literal
She [topic-は] crying boy [to-に] kiss [object-を] did [and-て] soothed.
泣いている男の子 is a relative clause modifying a noun: 'the boy who is crying.' Japanese forms relative clauses by simply placing the modifying clause directly before the noun, without any relative pronoun or punctuation — a feature that makes Japanese remarkably compact compared to languages that require 'who/which/that.' キスをする is the verbal idiom for kissing (you can also use the imported verb キスする), and なだめる ('to soothe, to placate') is one of those middle-frequency verbs every learner picks up after a year or two of immersion. The te-form chains the kiss directly into the soothing as a sequence.