وَإِذَا لَبَّى فَقَدْ أَحْرَمَ
Translation: Once the pilgrim says talbiyah, entry into iḥrām has taken place.
Idhā introduces the temporal condition, labbā is a past verb with an understood subject, fa-qad links and emphasises the result, and aḥrama is a Form IV perfect verb.
Its preceding context supplies intention accompanying talbiyah.