Before install failover cluster, you must select the hardware and the operating system on which SQL Server will run: https://learn.microsoft.com/en-us/sql/sql-server/failover-clusters/install/before-installing-failover-clustering?view=sql-server-ver15
Create and configure a failover cluster instance: https://learn.microsoft.com/en-us/sql/sql-server/failover-clusters/install/sql-server-failover-cluster-installation?view=sql-server-ver15
Install or upgrade a SQL Server failover cluster instance: https://learn.microsoft.com/en-us/sql/sql-server/failover-clusters/install/create-a-new-sql-server-failover-cluster-setup?view=sql-server-ver15
Considerations for deploying Always On availability groups: https://learn.microsoft.com/en-us/sql/database-engine/availability-groups/windows/prereqs-restrictions-recommendations-always-on-availability?view=sql-server-ver15
The steps for configure instance of SQL Server to support Always On availability groups: https://learn.microsoft.com/en-us/sql/database-engine/availability-groups/windows/getting-started-with-always-on-availability-groups-sql-server?view=sql-server-ver15
Reference for the creation and configuration of Always On availability groups: https://learn.microsoft.com/en-us/sql/database-engine/availability-groups/windows/creation-and-configuration-of-availability-groups-sql-server?view=sql-server-ver15