When arriving to Dzintari by train, walk past the Dzintari train station main building and straight under the bridge until you reach Dzintari Forest Park (Dzintaru Mežaparks). When the park is directly in front of you turn to the right and walk along Meža prospekts past Madonas iela, which is the street right on the edge of the park. From here walk another 100 meters or so along Meža prospekts and you will see signs guiding you to the property. Timetables and prices for the trains can be found on http://www.pv.lv/en/.
If you come from Riga by bus, the stop you need to get off is Dzintari and is on Meža prospekts right after the freeway bridge that goes over the train tracks. From there proceed as above along Meža prospekts.