My beretta's dash did not come with a gauge for Oil pressure so I went out and bought a mechanical one and my brother and I tried to find the correct spot to install the tube, We are clueless, Does anyone know where the point of installation would be for a oil pressure gauge on a 96 3100 beretta?

 

It would be much cleaner of an add in if you found a full gauge cluster with the analog gauges for everything. Then after you swap in a full gauge cluster, you just would have to replace the sending unit out for a "gauge/analog" typesending unit. If you insist on using the one you purchased, then you will need to unscrew the current sending unit and find a "T" to fit the block, sending unit, and "new" pressure sensor. Then assemble the "T" with original unit, new unit, and too the block. After that, wire it up as accordingly to the directions.

PS the unit is located by the starter and oil filter.
Hope this helps!!