DensityPlot[Sin[x + y^2], {x, 0, 2 Pi}, {y, 0, 2 Pi},
  PlotPoints -> 100,
  PlotLegends -> Placed[Automatic, Right]]

DensityPlot[Sin[x + y^2], {x, 0, 2 Pi}, {y, 0, 2 Pi},
  PlotPoints -> 100, ImageSize -> Medium,
  PlotLegends -> Placed[BarLegend[Automatic, LegendMargins -> 0] ,
     {{1, .5}, {0.1, .5}}]]