Use "hotspots". There is a tool bar that has the various shapes for this -
a circle and rectangle tool among others. it is on the "pictures" toolbar
(if this is not visible go to View > Toolbars > Pictures to turn the tool
bar on).
Then choose the tool labelled "Rectangular Hotspot", and on your image,
"expand" or draw the rectangle, holding down your left mouse button. Let go
of the mouse and FP will open the hyperlinks dialogue, where you put the
page to link to in the usual field. You can choose the usual options like
"tooltip" text and the "Target" of the page to open as with normal
hyperlinks.
Hope this helps.