Typically, you may picture crane operations as involving the large 'slewing' cranes that you see at building sites. However, 'crane Operator' is not just one job, but several, as different kinds of crane require different kinds of license. It may be that you only need to know how to operate one particular kind of crane, such as a vehicle loading crane, in which case you will need a license for that type alone. However, if you are doing more general work or more kinds of work, it may be worth getting a different level of license, which will allow you to operate multiple kinds of cranes, or perhaps even getting several licenses, allowing you to operate several specific crane types.
Whatever you decide to do there is a potential for risk to yourself and others, which you must account for. However, on the whole, if you have the correct training and license and apply the procedures correctly, crane operations should always be safe.
Crane operators are usually responsible for setting up the crane, too, so your training will cover how to do this correctly and safely.
A crane operator must have a steady hand and a level head: The top level of slewing cranes have capacities of over 100 tonnes, and so are potentially extremely dangerous, hence the plethora of licensing and other regulations surrounding their operation. As the operator of the crane, you carry the primary responsibility for ensuring that it is being operated in a way that is safe for you and others, including observing all the relevant health and safety procedures and risk assessments. The same applies to the process of setting up the crane.