Getting a SpeedTree model into and arbitrary DCC applications is a three step process. First, select or create a model in the SpeedTree Modeler. Second, export the model using 'File→Export mesh…'. Third, import the generated file in the application of your choice. See below for a detailed explanation of these steps.
The first step in the process is to use the SpeedTree Modeler to create the model. This can be as simple as opening a library model or as complex as creating a tree from scratch. Some SpeedTree features such as detail maps, branch intersection blending, and wind may be difficult to implement in applications not supported directly by SpeedTree; however, all geometry and base texture layers should work with either the .fbx or .obj formats.
Once the model is complete, select 'File→Export mesh…'. In the ensuing file selector, select 'Autodesk FBX' or 'Wavefront OBJ' from the combo box labelled 'Save as type' and pick a filename for the export. These formats are the most likely to import successfully into DCC applications.
Use the standard import mechanism in the DCC application to import the model. The geometry and base texture layers should be correct; however, it will likely take some manual clean up to implement things like specular reflections and translucency on leaves.