Travel between Italy and the Netherlands (where Amsterdam is) is treated as a domestic trip - no border control, and usually both are covered by your visa/residence permit.
However, very few visas are LTV. If yours is it might not be valid for the Netherlands. Again, there are no border checks, so in practice, if you're not stopped inside the Netherlands, such a trip (while illegal) is possible.
Please upload a scan of your visa or residence permit (permesso di soggiorno) so we can say for sure. If you have a residence permit, you can go to the Netherlands 100%
UPDATE: you have a full residence permit, so you do not Need a visa for Amsterdam. When Boarding the flight, simply show your passport and residence permit if asked - though very often they only care about the Boarding pass