I have a self propelled Toro walk behind that does not have a throttle control. Stalls out if grass is just a bit high. How/ where do I adjust throttle

Murray push mower 6.5 electric start doesnt work

Most new mowers do not have a throttle adjustment, the motor has a govnor that helps the motor speed up when the load requires it. The first thing you should check is that the blade is sharp which makes it easier to cut the grass. If the grass is still too high for the motor to keep up, it's usually easier to raise the deck (lower the wheels) so you are not cutting as much grass on each pass. Then lower the deck to where you want the grass height to be and make a second pass.

You can't and you don't. The engine speed is controlled by the governor. If the engine has a Briggs Quantam engine, you may be able to "add" a throttle cable w/ lever control. They say Murray makes a good one. Some of the Briggs still have the hardware on the carburetor to make this possible. You will need to look at your engine and carburetor set up. No push/walk behind mowers have the throttle cable/lever anymore....just riders. It is most likely part due to EPA mandated emission rules which have become quite stringent in the past few years.