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I don't think the START button is a power button. It is meant to be used to e.g. start a photocopy running, once the Epson printer is actually turned On.
Look for the On/Off button, or a power switch, to power On the printer, instead.
Power switches are usually near where the power cord goes into the printer.
On/Off buttons are usually large and prominently labeled as such, if they are on the control panel of the printer.
As for where the control panel of the printer is: it's the array of buttons, and the display, on the front upper surface.
But in this case, for your model of printer, the control panel is basically the upper part of the front side. Lowering the control panel... you just need not to force it downward, is what that instruction means. There is a release catch under its lower edge... when it has been raised. Since you just received yours, it probably has not been raised, so that does not apply. "Raised' means, tilted upward so that it's less on-the-front-of-the-machine, and more like on the upper front corner facing upward and forward both.