For beginners animating an armature (skeleton) 3D model, start with keyframes for bone positions in your software—keep motions simple and focus on one bone at a time.
Select a bone, adjust its rotation/movement to pose the model, then add keyframes (markers that save bone states) at the start, middle, and end of the motion. Your software will automatically fill in the movement between these frames.
Try basic actions like waving in free tools like Blender: Move the forearm up at frame 10, down at frame 20, and add keyframes at each step to preview the animation.
Stick to one bone initially instead of the whole body—this helps you master keyframes and rigs without feeling overwhelmed.