How do the engines work?

How do i use the engines to smash planets into each other?

Please search, there are multiple threads on the first page that explain this.

But they dont explain how to use them. By now i got like 20 engines but they still dont do anything.

Check this post/thread:
https://forums.uberent.com/threads/how-do-i-use-halleys.51579/#post-791185

If you dont see those symbols for a planet the planet is too big and can be moved.

locking this thread, as it is 100% redundant