Please go to the UCSB MathWorks page to download the software. Click on the "Get started today" link in the box, where it says Download Matlab. On the next page, Log in with your UCSB NetID. Once you've logged in with your NetID, you will need to either create an account with your UCSB Email address or if you already have an account under your UCSB Email, log in with that account in order to download and receive a license.
If you haven't logged in before, create a new MathWorks account using your UCSB Email (you will need to create a passwrod for the account), to gain access to a Matlab license.