There's many ways to do it, but the mains ways are:
1) attach them all in Spine, then just show the appropriate one (simple, but can be tedious for many attachments),
2) generate attachments at runtime, possibly even packing the atlas at runtime (most complex, best performance),
3) BoneFollower (simple, but performance isn't as good, though that might not matter).
For more on #2, see here:
Runtime Skins - Spine Runtimes Guide