Coordinates[] pts = Generate.RandomLocations(4);
ScottPlot.Plottables.Markers m1 = formsPlot1.Plot.Add.Markers(
    pts,
    MarkerShape.CircledDot,
    20);
m1.MarkerLineWidth = 3;

pts = Generate.RandomLocations(4);
ScottPlot.Plottables.Markers m2 = formsPlot1.Plot.Add.Markers(
    pts,
    MarkerShape.RingedCross,
    20);
m2.MarkerLineWidth = 3;

pts = Generate.RandomLocations(4);
ScottPlot.Plottables.Markers m3 = formsPlot1.Plot.Add.Markers(
    pts,
    MarkerShape.RingedEks,
    20);
m3.MarkerLineWidth = 3;