One can follow the steps below, to get a Subscription License.
a) One has to Login to the Lattice Website using his/her login credentials (www.latticesemi.com)
b) You can contact your Local Lattice sales or Buy it online.
Visit the Lattice Online Store.
Purchase the DIAMOND-E-12M product from the list. You will get an email to your registered email address, with the details to request the License.
Or, you can contact your Local Lattice Sales to purchase the same from this link
c) Once you have purchased a Product/License as mentioned above, visit this link .
Enter the email ID and password as shown in Figure 1 below

Figure 1
d) Click on Request a new license

Figure 2
e) Enter details, NIC address and software serial number that is provided in the email.
Select the type of License (Node-locked or Floating) as shown below
Enter the NIC no. and the Flex ID (for floating License only)

Figure 3
After entering this, the user will get the License on their registered email add.
Note that when running the Lattice Diamond Software in a floating set-up, users will need to buy the USB dongle to use the Active-HDL simulation tool. Refer to this FAQ for details on how to get the USB key dongle.