Hi,

The most important thing to keep in mind is that you need to first process the upgrade to be able to have the latest version allocated to your account.

To process the upgrade from your 2019 version to the 2021 one please follow the below steps 

1. Log in into your SDL account 

2. Click on Products&Plans - Licenses 

3. Click on the blue ribbon that holds the message 'You have 1 upgrade available'

4. On the page that appears click on Upgrade button again 

5. Once all done return to licenses tab where the 2021 license code will appear. 

For a step to step guide with images please use this link - https://community.sdl.com/product-groups/translationproductivity/w/customer-experience/3183/how-to-install-and-activate-studio-2021-and-studio-2019-side-by-side
Please note that the 2019 will continue to work as long as you have it installed on the same PC with the 2021 version. 

 If you experience any technical issues please contact the licensing and installation technical department 

Kind regards,

Elisa

Some excellent advice here from Elisa Maxim.  FLEUR SCHUT and myself also discussed this question at the Elevate conference so we've put the video here as it perhaps covers some areas to think about not mentioned in the post above: