how to i figure out how many amps  my generator is putting out?

The people answering this questions are stupid. The generator detects the load and either increases RPM  or decreases RPM to supply the amount of wattage needed to power whatever is plugged into it. It had a maximum wattage rating. Wattage divided by voltage is amperage. It doesnt constantly put out its max amperage. It changes based on what is plugged into it.

What generator?? 

Use an ammeter.Use a clamp ammeter.Not all multimeters can measure amps the way you need it.

Take it to an Autozone store. They have the equipment to run it up and test the output. The test is free.

You will have to place an amp gauge in between a battery post and it's cable to find out. NOT a multimeter. And if the battery is fully charged, it will show minimum amperage output. Turn on all lights and accessories get a higher amperage output. The best way to see if your charging system is operating right is to simply use your multimeter across the battery while the engine is running and it should read 13 volts or up. Turn on the AC and all lights on and it should show around the same.

You need a clamp on DC ammeter.

Those cheap ones, as I am 96% sure you have, won't do it. These are $ but easier/safer to use than a regular inline type .Clamp it 'round the big lead from gen, turn on. In meantime, using present MM,   start car, check voltage drop from gen terminal to battery, battery voltage, drop across ground leads from battery. No lead should show more than .2 volts drop or bad cable or connection. A vehicle with a Generator should show 7.5 volts at battery  (14,4 if a 12 volt unit.) If U can do it Safely; should measure drop from battery to starter on starting. Again, no more than .2 volts drop,  or problemo.

Or, take it to an auto electrical shop. Might do it for free.

Note, Also, to check Max you must connect the DC clamp -on, turn it on, have yore wife start the car while You Read. That initial high reading is it, it will go down quickly.

 Also , the gen might Not put out its rated max to yore battery. With a generator, you will also have to open throttle a bit to see. It can't put out full at idle. Can be properly tested for full rated current on a carbon pile load at an auto el. shop. A low reading at your car Can be slipping belt, bad connections, bad grounds, marginal battery, bad external mechanical regulator, etc.

EDIT: The standard old mechanical  meters that require a shunt to place them in series are very expensive and unnecessary in the 21st century. Connecting one Safely and properly isn't something to be described, here. Try You tube; better to Forget It, use the clamp on. I do on hi ranges. I bought a  5/50 amp antique unit cheap at  swap meet,  but its Necessary additional  Shunt cost $$. 

Google how to use a multimeter and check it out. If it shows almost 14V you're good to go. 

It only puts out what is demanded of it. If the load is low, it will have a low output. If the load is high, it will have a high output. So, what you need to do is put a known load on it and then measure the output to see if it matches the load or not. 

Use OHM's Law. E= I x R.

A good multimeter will come with an amp clamp to put around the positive battery cable to sense the amperage. If the voltage output at the battery posts is 13.7 or higher with the motor at 2000 rpm the alternator is good.

Take the equipment to a smart person and ask them to show you what to do.