Start from your rigged character and File > Import/Export > Export FBX in FBX 200900 format (character in t-pose, with Y-up orientation, facing +Z)
Select a Motion Model - Mixamo has hundreds of online motions - Many more being added each week
Design & Synthesize Motion using built in sliders and controls
Upload your FBX model - Automatic mapping for standard joints naming conventions
Final Preview & Download - Preview to your heart's content - Only download when you're satisfied, in FBX format
File > Load Scene > Load Items from Scene, and select the downloaded FBX file back into LightWave (Be sure to select "Merge only motion envelopes" in the loading window. A skeleton (B) identical to the one of your character but with motion applied will be loaded in the scene.
Copy motion onto your character skeleton Adjust the timeline to match the number of keys downloaded. In the Scene editor select all the keys on each bone of skeleton (B) and copy them to the corresponding bone on skeleton (A). At this point you can delete skeleton (B).