You will need an account to sign in to ArcGIS Pro. If you don't have an account through your work or school you can sign up for a free trial account here: https://www.esri.com/en-us/lg/training-and-services/learn-arcgis-education-trial
If you have an account but are having trouble licensing ArcGIS Pro with it, see the instructions here: https://community.esri.com/t5/learn-arcgis-documents/frequently-asked-questions-for-learn-arcgis/ta-...