To import Move One animations into Unreal Engine, drag and drop the .fbx file into the Content Drawer and click Import.
To retarget the animation, follow the below workflow:
Using Unreal 5.2
Import the animation using the above steps.
Create IK Rig both for source and target rigs (skeletal mesh), set target chains (both legs, both arms, spine), set the hips bone as the root
For the target IK Rig setup Full Body IK Solver, add Goals to the feet. Add settings to the upper leg bones and adjust Preferred Angles so the knees bend into the right direction. Add settings to the hips bone, increase Stiffness
Create IK Retargeter with the source and target rigs. In Root Settings adjust Translation Offset on Z if needed. For both leg chains adjust Static Offset of IK on Z if needed.
In the scene add source blueprint.
Add the target rig blueprint to the scene (created on step 5)
Add target blueprint as a child of source blueprint