Plot[
{x^2 + 2 x + 1, x^2 - x + 5}, {x, 6, 50},
Axes -> False, Frame -> True,
FrameLabel -> {"I [\[HBar]]", "E [MeV]"},
PlotStyle -> {Black, Thick},
ImageSize -> Large,
PlotRange -> Automatic,
PlotLegends -> Placed[{"Th.", "Exp."}, {0.15, 0.75}],
Epilog -> {
Inset[Framed[Style["Top Right", 20], Background -> White], {45, 2300}],
Inset[Framed[Style["Bottom Right", 20], Background -> White], {45, 300}]
}
]