!. If your actual applied load is uniform across the width of the beam then you can use the standard beam equations for your plate.
Also, If your applied loading is concentrated across the center of the beam; then you will need to perform one analysis for a distributed loading only for the beams weight. and a second analysis for the beam with the applied center loading only and then sum the results of those two analyses to get the total max stress and max center span deflection of the beam under those combined loads.
2. If your loading is also is evenly distributed along the length of the beam, then use the standard beam equations for that arrangement and use the combined total of your applied load plus the total beam weight in those formulas.