What namspace and I missing for Serilog?

I am able to use LoggerConfiguration() in my C# code with various Serilog Sinks but my compiler is complaining about the specification of my use of ".WriteTo.File". I am confused because I have ben able to use this specification in another demo solution. I wonder if there is some sort of Assembly I need to add as a reference. I have run "Install-Package Serilog.Sinks.File" from the "Package Manager Console" but that did not seem to have any effect or change.

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What directive am I missing or what assembly reference do I need?

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I tried to figure this out via online documentation but I can not find the result.