You'll need to get to the bus station in Irkutsk and get on a bus or minibus that goes to Listvyanka. On the window of that bus you'll see the sign that will say (Listvyanka). Get off at the end stop and for 5-10 minutes walk back along the main street (shoreline) to the cafe 'Listvyanka Club', near the Information Center kiosk. Then turn right and follow the street (Sudzilovskogo). The Olga's guesthouse is shortly there.