Hi DonFrag, the workflow of using spline to spawn instances would be:
https://i.imgur.com/KTrUtVc.jpg
1. Convert the mesh you want to instancing on spline to HISM or ISM
https://i.imgur.com/5NDuLfu.jpg
2. Select an actor with spline component
https://i.imgur.com/5Izz1aS.jpg
3. Click “Spawn Instances” button to spawn instances on selected spline points.