The figure and animations must have corresponding “bone” structures.
If they match, you should be able to right click the Animations and select the figure as a skeleton.
If they are not the same skeleton, but have the correct bones - you can coax them to work together…
Open the skeleton for the figure the animations were made for (usually Mannequin) - and click [Retarget Manager] at the top - select Humanoid for the rig type and save the skeleton.
Do the same for the skeleton that comes with the figure you want the animations to work with.
Then you can right click the animations and select [Retarget Anim Asset → Duplicate … ]
and pick the skeleton of the figures you want them to work with.
It will create a copy of the animation that is set to that skeleton.
Make sure you get all of them (particularly the Anim Blueprint) since you will need a working copy of that to select in any Character blueprint you make using the figure.
(Made a quick video showing how - since it sounds more complicated than it is)