To use a public cloud engine, you normally need Ducats. If you are lucky, you can even find free engines, but other users might take them away by outbidding you. Click here to get Ducats.
If the engine has a green dot symbol on the left, you can double-click to start using it. Engine pricing has three parameters:
During analysis, you never pay more in advance than the price of a single minute. You can stop at any time if you are not happy with the engine. You can try out many engines quickly without any risk.
If the engine has a yellow dot symbol on the left, it is in use, but you may try to outbid the current user. Note: If an engine is already in use, every bid is charged an additional fee equal to the current minute rate, even if the bid does not succeed. This protects the current user from destructive bidding where people just want to take the engine away.
If your bid does not succeed, you can "queue" it. This will automatically load the engine if the current user stops. A board window with a given position will then automatically start analysis with that engine. An engine where you queued a bid is written in red.
If the engine has a red dot symbol on the left, someboday has booked it at the reliable rate. You cannot outbid the current user. However you could again queue a bid at any rate, see above.
When you have acquired an engine, the engine connection window will open. If you close it by clicking "Stop", the engine will cease working in your board window and all payment stops immediately.