In order to acquire items in Ingress you have to hack portals. The level of items you obtain is influenced by the level of portal you are hacking however it is not directly correlated. So you can receive higher or lower level items than the portal level. When hacking enemy controlled portals you will also receive a small amount of Action Points (AP) but less (if any) items. However, you will also take an amount of damage from the portal to your XM pool.
To hack a portal you must first be within action range, which is within 40m of the portal. Once you are within action range of a portal you should click on the portal and then click ‘Hack’ in the portal menu. The action of hacking will take a short amount of time as it will hit the game servers, but you can leave the action range while hacking and still receive items.
When hacking any portal you have a chance of receiving a portal key. These keys are important as they allow you to remotely recharge the resonators on a portal as well as link to the portal from another portal.
There is a 5 minute cool down on hacking a portal and if you hack a portal to many times in an undefined amount of time it will cause the portal to burn out and prevent it from being hacked for an extended period of time. If you attempt to hack a portal that is still cooling down you will receive a notification with approximately how long until the portal will be available again. This timer rounds up to the nearest minute until you get to under a minute in which case it rounds up to the nearest 10 second mark. To burn out of a portal it takes around 5 consecutive hacks.