Online offer was cheaper 34.40 € but you don't have time or the same offer anymore you can purchase at the tourism info store at the centraal station I think is 38€(I highly reccomend to buy it online because these offices are always crowded and you waste your time) The card includes free entrances for most of the important museums, a free canal boat tour and free transportation plus some free coupons and discounts even you can use them after the card expires(bus-tram-metro) At the end you save a lot... Dont forget to used the book
After picking our cards we went down to the metro station in Centraal Station and we purchased also 1 day transportation card (7€) for the rest of our trip. It worked perfect, You must show your card to the scan machine at the tram/metro/bus both coming in and out.
When you purchase the IAmsterdam card, you recieve a public transportation pass corresponding to the number of days your card is for. It comes out to be a good deal, as you can hop on and off the tram systems as much as you'd like in this time frame, and even use the Metro if you really must.
The ticket is active from the moment the first conductor stamps it. From then on, you must have it with you at all times and either present it to the conductor or the ticket check kiosks throughout the tram.
Just be sure to have it with you at all times!!!
If you're going to be in Amsterdam for at least 24 hours, get an I Amsterdam pass which can be purchased at the tourist office (VVV). It is available for 24, 48 or 72 hours. A 72 hour pass cost 53 Eur. You get a pass for the tram as well as separate card for free entrance to most museums and other attractions --one notable exception being the Anne Frank House.