The Custom SSIS Tasks package is downloaded from TARGIT's Download Center.
Try to download the correct version according to your SQL server version.
Note: Even if you should have a later SQL Server version, e.g., SQL 2022, you can still download and install the latest TARGIT Custom SSIS Tasks package. Just needs a little tweaking - see the Deployment Target Version section below.
Once downloaded, simply install the package from the .exe file. Make sure that you close Visual Studio (or Data Tools) during the installation.
When you reopen an SSIS package in Visual Studio (or Data Tools), you will now see the TARGIT Custom SSIS Tasks in the SSIS Toolbox:
Deployment Target Version
If the TARGIT Custom SSIS Tasks does not show in the SSIS Toolbox, it may be due to your SSIS project being of the wrong target version. E.g., if you install the 'TARGIT Custom SSIS Tasks for Microsoft SQL Server 2019' in a SQL Server 2022 environment.
To correct this, in the Solution Explorer in Visual Studio (or Data Tools), open properties for your Integration Services Project and change the TargetServerVersion property to the version that matches your TARGIT Custom SSIS Tasks package:
Setting the TargetServerVersion will not limit where e.g., a Period Table can be deployed. Even if the TargetServerVersion is set to SQL Server 2019, you can still use the custom tasks to produce tables in e.g., a SQL Server 2022 database.