You can also attach Actors to Skeletal Mesh Sockets by way of the context menu within the main editor viewport. This does not require Socket Snapping to be activated, and as long as you know the name of the Socket you want to attach to, this can be a very fast way to make the attachment. As with the Socket Snapping technique, this is best suited to making attachments on Skeletal Meshes that have already been placed in the level.
Right-click on the mesh you want to attach. Choose Attach To > [Name of your target Skeletal Mesh]:
From the flyout menu that appears, choose the name of the desired Socket.
The Actor snaps to the location of the Socket.
This method only works for attaching to a Skeletal Mesh asset and will not work for attaching to a socket located on a Blueprinted asset.