Travel to Sheffield
The closest international airports are Manchester and Leeds-Bradford, both of which are well connected to Sheffield by train. The journey takes about 1 hour once you've got from the airport train station to the city train station. East Midlands Airport is also about an hour away by train. The nearest station is 5 miles from the airport (East Midlands Parkway) and you have to take a taxi to get there. London also has a regular direct train to Sheffield but it's much further away, about 2.5 hours from St Pancras station, plus it could easily take 2 hours to get from any of the London airports to St Pancras.
Find UK train info and book tickets. Tickets are almost always cheaper when booked in advance, sometimes a great deal cheaper and you can opt to pick them up at the station of departure from the 'Fastticket' machine using the payment card and a reference number.
Travel within Sheffield
The train station in Sheffield is about a 20-25 minutes walk from the conference venue, mostly uphill. You can also catch a tram from the back of the train station that does a loop of the city centre.