So to install Nuget Packages For Multiple/Sub-Projects in a Solution.Just Right Click Solution.
Manage Nuget Packages
So To share or Install Multiple Nuget Packages in Start Project Go to.
Here you find all Installed Nuget Packages of Root Project(if already Installed Nuget Packages)
or If you are not installed already install them(it will Ask For to which projects should apply the Nuget Packages Tick for projects Which you need To apply).
If you already installed Nuget Package for Root Project You Will See Manage Button.
Click it Now You Will See The Following
Now Choose Which Projects you want to share the Nuget Package and apply Hit Ok
According to you selection it will apply/share the nugets to all sub-projects .
Its Done
Please Comment Below For Any Further Doubts.