This is a regular verb. It follows the conjugation pattern of the verb partir.
Present:
A Ana resume o artigo em poucas frases.
Ana summarizes the article in a few sentences.
Preterite:
O Miguel resumiu a reunião para o chefe dele.
O Miguel resumiu a reunião para o chefe.
Miguel summarized the meeting for his boss.
Conditional:
A Clara resumiria o relatório de forma mais clara.
Clara would summarize the report more clearly.