This package appears to have a custom/proprietary license agreement, and ProGet cannot be automatically determine the license type. You'll need to assign a license type to the URL to allow or block packages with this license.
To install EPPlus from the command line, run the following command:
nuget install EPPlus -Version 4.5.3.11 -Source https://nuget.perfectxl.com/nuget/default/
To install EPPlus from the Package Manager Console within Visual Studio, run the following command:
Install-Package EPPlus -Version 4.5.3.11 -Source https://nuget.perfectxl.com/nuget/default/
For projects that support PackageReference, copy this XML node into the project file to reference the package.
<PackageReference Include="EPPlus" Version="4.5.3.11" />
Create advanced Excel spreadsheets using .NET