Visit https://beta.sketchengine.co.uk/ and click Institutional login on the right
Type a few letters from the name of your university or institution. When you see the name, select it by clicking it.
Click Continue and the login page of your university or institution will open.
Use your university or institutional login details to authorise yourself with your university/institution.
After successful authorisation, you will be redirected back to Sketch Engine as a logged-in user and you can start using it.