Dependencies:
.NETStandard 1.3
NETStandard.Library (>= 1.6.1)
Newtonsoft.Json (>= 12.0.3)
The only supported frameworks are those that conform to .NET Standard 1.3 - according to
Microsoft[
^], that means your application needs to target .NET Framework 4.6 at a minimum.
If you can't change the target framework of your application, then you can't use that package.
NB: .NET Framework 4.5 is quite old now - it was release 8½ years ago. Support for 4.5 and 4.5.1 ended in 2016, so you'd need to be on at least 4.5.2 to continue getting security patches. Most machines should be on at least 4.7.2, and preferable 4.8.