To import an .obp file (object preset) into your object library, first enter your object library. On the 'Create' palette, next to the word 'Create,' there is a pale grey triangle pointing right. Click on this triangle. You will see the Object Library appear. Please see the screenshot below for details.
In the Object Library, you will see a preview in the upper left, one or more folders on the left and objects in various boxes in the middle and right. On the bottom, you will see the choices 'Add Delete Import Export.' Click on 'Import' and you will have a browse menu. Browse to the .obp file you wish to use, highlight, and click 'Open.' You will now see the object preset in your object library. You can also export object presets and maintain the organization of your library in this screen.
To bring the object into your Bryce Scene, highlight the object and click the checkmark in the lower right of the Object Library. The object should appear in your Bryce scene.
A Bryce Object Preset (.obp) is *not* the same as an object file (.obj). The Bryce Object Preset file only works in Bryce and supports textures as part of the file. An object file (.obj) is a geometry file that usually only includes the UV mapping. If you import a .obj file into Bryce, you will just get a model without any textures.