If using Rokoko sample animation, export as FBX format, binary, Mixiam skeleton, FPS se
Import source animation fbx file (i.e. without mesh, just action)
Import target T post mesh object (need both mesh layer and T post skeleton, i.e. 2 layers)
On Source layer, R click → Rigging tag → Character Definition → Open Manager → Extract Skeleton (check if all joints Ref change to Yes)
On Target skeleton (green color one) layer, add Charccter Definition as well and extract skeleton, but also click Create Solver (a Character solver tag created in the layer)
Drag the character definition tag from the source animation in Target’s solver tag →
To Source character box. Then the source action apply to the Mesh character