1
general::
Understand, be informed about or be involved in a particular situation or activity. For example, The new ambassador wanted to be in the picture for every event, small or large. This term is Also used in such locutions as put someone in the picture, meaning "to inform or include someone," as in Put me in the picture about the new staff, or out of the picture, meaning "to be left ignorant of or excluded from some activity," as in The local authorities were out of the picture when it came to drug dealers. [Early 1900s] Also see GET THE MESSAGE (PICTURE).
American Heritage Idioms
2
general::
Phrase(s): *in the picture
Fig. well-informed; aware of what is going on. (*Typically: be ~; keep someone ~; put someone ~.) • Please, keep me fully in the picture. • John found out about the plan. He’s in the picture, so take care.
McGrawhill's American Idioms And Phrasal Verbs