Method 1: Download Free Spire.XLS and unzip the package somewhere on your disk to find the “BIN” folder. Free Spire.XLS has the DLLs compiled for multiple versions of .NET Framework as well as for .NET Core and other platforms. Choose the DLLs from the folder that you exactly need and add them as dependencies in your project.
Method 2: Create a .NET application in you Visual Studio, and install Free Spire.XLS directly through NuGet. NuGet package manager will automatically install the correct version that fits in with your application.