The image you've attached shows a Polymorphic VI with selector visible.
The question you've posted is a little unclear, but if you want to create a polymorphic VI, hopefully that link is helpful. The menu to create one is via File > New... > Polymorphic VI. You might also find Building Polymorphic VIs helpful.
Selector icons can only be added to polymorphic VIs. You must create a Polymorphic VI (see the second link) then add the appropriate other VIs (probably the ones you're describing as your "new subVI"s) to that polymorphic VI.
To expand a bit, the Selector will choose which specific Polymorphic VI you're using. Each selector element will correspond to a different subVI. The selected value will dictate which subVI runs- you can't use it like an "input" to a single subVI.