get a handle on something, to

To succeed in dealing with a difficult problem. Dating from the mid-twentieth century, this slangy Americanism alludes to coping with a cumbersome object by attaching a handle to it.

However, “handle” has been used both figuratively and literally in several
ways for many years. “Most things have two Handles; and a wise Man takes
hold of the best,” wrote Thomas Fuller in Gnomologia (1732). Further, “handle” has been a colloquialism for a title, and by extension a name, since
about 1800. The current saying, on its way to becoming a cliché, thus can
allude either to getting a secure hold on a slippery problem, or to identifying it correctly by naming it. A synonym for the former sense is get a grip on
something, meaning to take a firm hold on it. See also GET A GRIP.