Huh? It sounds like the assignment is, given a node in the target list, insert a new node into it. Otherwise you'd have an assignment like "insert in sorted order"
So, given a target node called 'target' and you want to insert 'toBeInserted' you generally need to:
A) Remove the toBeInserted node from whatever list its on
B) Add it to the new list before or after 'target', whichever is appropriate.
And the general steps for removal are (with the current node bing 'this'):
set prior's next to this next
set next's prior to be this' prior
set this' next to this
set this' prior to prior
and to insert before target you do something like this:
this' next is target
this' prior is target's prior
target's prior is this
this' prior's next is this
(to insert after is similar, but slightly different of course)
Hope that helps!
(note to moderator's: trying not to do the assignment, but to explain it. Walks a fine line, there)