By activating the SIM card at you get 1 GB free trial during 30 days.

After the trial there are three subscriptions to choose between; Small (0.1GB) Medium (0.25GB) or Large (2GB). You can decide which subscription that will suit you based on your consumtion during the 30 days trial. 

Select "Proceed to payment" and enter your payment information and select "Subscribe" 

The subscription starts after the 30 days trial. If you run out of data before the 30 days you can manually start the subscription immediately. Note that if you are out of data the SIM card has been deactivate. To get it to work asap after activating the subscription you can remove tha battery and insert it back so it restarts and connects to the network again.