Starting from your character in 3dsMax, select the character skeleton and export in FBX format (character in t-pose, default export settings of FBX plugin, Y-up). IMPORTANT! Please remove all IK controls. This is also a general rule: Mixamo only needs the FK joints of your rig. Make sure your character is in t-pose on frame 0 of the scene.
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 - Most likely your CAT character will be automatically mapped to our standard skeleton
Final Preview & Download - Preview to your heart's content - Only download when you're satisfied, in FBX format
Import the downloaded FBX file back into 3dsMax. File > Import and Select "Update Scene" in the FBX import plugin. Select take mixamo.com and check the "Fill Timeline" to update the timeline of your scene. Exportthe scene in Collada .DAE format, with Z up.
Import the animation on a playable character Open ShiVa Editor, General desktop, in the DataExplorer Module, select Import > Model, in "file to import", select the character exported from Max. Check Convert from Z to Yup axis and uncheck Animation in the filter part. Double click on the model to open it, In the Scene Viewer, select Display > Skeleton to show the skinning (the pink lines). To import the animation, select Import > AnimClip in the DataExplorer, check Convert from Z to Y up axis option. Drag'n'drop the new resources directly on the selected mesh, you will be asked to create an AnimBank, click Yes. To see the result, In the top left area, load the AnimBank Editor, Select AnimBank > Open and select the newly created animbank in the drop down list (auto-created animBank will inherit the mesh name). Double click on the first field, the animation is playing!