Specify Both X And Y

This web site builds the control from code behind but you could also grab it from the toolbox, this sample also uses a ViewModel to populate the properties of the control(s) in this sample.

sample image

View model

using CommunityToolkit.Mvvm.ComponentModel;
using LiveChartsCore;
using LiveChartsCore.Defaults;
using LiveChartsCore.SkiaSharpView;

namespace ViewModelsSamples.Lines.XY;

public partial class ViewModel : ObservableObject
{
    public ISeries[] Series { get; set; } =
    {
        new LineSeries<ObservablePoint>
        {
            Values = new ObservablePoint[]
            {
                new ObservablePoint(0, 4),
                new ObservablePoint(1, 3),
                new ObservablePoint(3, 8),
                new ObservablePoint(18, 6),
                new ObservablePoint(20, 12)
            }
        }
    };
}

Form code behind

using System.Windows.Forms;
using LiveChartsCore.SkiaSharpView.WinForms;
using ViewModelsSamples.Lines.XY;

namespace WinFormsSample.Lines.XY;

public partial class View : UserControl
{
    private readonly CartesianChart cartesianChart;

    public View()
    {
        InitializeComponent();
        Size = new System.Drawing.Size(50, 50);

        var viewModel = new ViewModel();

        cartesianChart = new CartesianChart
        {
            Series = viewModel.Series,

            // out of livecharts properties...
            Location = new System.Drawing.Point(0, 0),
            Size = new System.Drawing.Size(50, 50),
            Anchor = AnchorStyles.Left | AnchorStyles.Right | AnchorStyles.Top | AnchorStyles.Bottom
        };

        Controls.Add(cartesianChart);
    }
}

Articles you might also find useful:

Cartesian chart control
Line series properties