After being told 'Please, have a seat,' I sit down in the chair.

Literal

'Please, sit please [quotative-と] say-[passive-れる][after-から], chair [in-に] sit.

Narrative present tense, typical of reflective/instructional writing. 言われてから uses the passive 言われる 'to be told' combined with ~てから 'after doing.' The passive makes the speaker the experiencer of being told, while ~てから establishes temporal sequence. どうぞ is a stock politeness formula inviting someone to proceed with an action. The sentence mixes direct speech in quotes with narrated action.