If you want to work with online CAT tools, such as SmartCat, XTM, Crowdin, Coach, etc…, just go to the Language&Settings tab and select the “Custom” option in the CAT tool section.
With this option checked, also select the keyboard hotkey combo that your CAT tool uses to copy the source segment into the target segment. Usually, this is Ctrl/Alt+Insert, but it can vary depending on the CAT tool you are using.
You can now work with your online CAT tool just like you would with an offline tool: just open your segment and press Ctrl+Space to machine translate its content.
Note: This works well in some CAT tools, such as SmartCat, Crowdin or XTM, but might have limited functionality in other tools (e.g. WordFast Anywhere) and not work at all (MateCat). If it does not work, simply open your segment, select all text in it (usually the Ctrl+A command) and press Ctrl+Alt+Space to translate selected text only = translate everything in your segment, because you have selected all text.
P.S. Yes, I know the picture is NOT funny… but we couldn’t resist anyway… 🙂