In the Piano Roll Window of the track you wish to tune:
Upper left, just below the pointer/pencil/erasure, there are 2 blue rectangles. The lower one by default indicates Notes/Vel.
Click once and choose New Value Type.
In the dialog box under "Type" choose "RPN."
Under "value" choose "Fine Tuning."
Under "Channel" choose the desired channel.
Make certain the pencil tool is selected and the erasure deselected.
Click in lower portion (controller pane) of Piano Roll window to set a new pitch. (If controller pane is not visible click icon at top of Piano Roll. In my view it is the 8th icon from the right.
From here, for me, it's make a guess and click, listen, control z to undo, make a better guess, continue refining until it sounds right.