A web search will show how to do it. But the calculations are fairly simple. There are 60' (minutes) in degree and 60" (seconds) in a minute. S57°18'05" = 57 + 18/60 +5/(60*60) = 57+ 0.3+0.001388 = 57.301388
and E 40.00. OSM also uses minus degrees for locations west of the Greenwich meridian and decrees degrees south of the Equator. so -57.301388 (S) and + 40 (E). This is a park near the where i live http://www.openstreetmap.org/#map=18/52.33182/-0.17130 if you copy that link and edit with the calculted calculated figures it should work for you.