Keywords' association with the current topic can rapidly be done using the check-box in front of the keyword.
To rapidly manage every topics associated with a specific keyword, select the keyword then click the "Associated topics" button in the "Keywords" group of the "Home" ribbon tab to open the "Manage keyword association" window.
Manage keyword association window
This window lists all topics within the project and adds a checked box before the caption of the topics associated with the currently selected keyword.
To associate the currently selected keywords with additional topics, check the boxes before the caption of those topics. Un-check those boxes to remove the association.
To save the modified associated topic list, hit the OK button at the bottom of the window.
See the How to manage the association between a keyword and topics step-by-step guide.