RealFlow can work with virtually any 3D program, but every program has its axis setup. Some programs use the Y axis as the vertical axis, others the Z axis. If the axis setup is not correct than all imported and exported objects – including particles – will be tilted around 90°. Change the setup under

File | RealFlow > Preferences > General > Miscellanea > Axis Setup.

Here are your options:

YXZ (Lightwave, Cinema 4D)
ZXY (3ds Max, Maya)
YZX (XSI, Maya, Houdini)

Furthermore, you have the possibility of changing between a local (upper image) and a global (lower image) coordinate system with this button of the icon bar:

Browser not supported