If you haven’t already, make sure you’ve received or at least applied for an Altium license before starting the download procedure, see Getting an Altium License
To download Altium:
Go to: https://www.altium.com/products/downloads?utm_source=altiumdatabase&utm_medium=email
Select the version of Altium you would like on the left. If you are familiar with a particular version of Altium, choose that one, otherwise, choose the newest one. Click on the Online Installer link to download the installer.
Follow the steps of the installer, and leave the options defaulted unless stated otherwise.
You will need to log in to your Altium account before you can start downloading so if you haven’t already, make an account and apply for a license. Login.
Once the installation is complete, run Alium
You will be brought to the License Management page upon start-up. There will be a list of available licenses. Select one of the Licenses with Product Name: Altium Designer and Status: OK. Click ‘Use’ to use that license.
If you don’t see a valid license, ensure you complete the steps in Getting an Altium License. If the issue persists, talk to a team member.
Now that you’ve activated you license, you can close the licenses manger window and proceed to