Which version of Windows are you running?
On Windows 10 it should already be preinstalled for example :)
Okay, you can check beforehand in the Control Panel in the section where you can see all your installed programs or uninstall them. There search for ".NET Framework" and see if 4.8 is installed.
You can also directly download it from Microsoft: https://support.microsoft.com/de-de/topic/microsoft-net-framework-4-8-offline-in...
Let me know if this helps!