Please delete this, posted and then found the answer

 

That’s the windshield washer fluid reservoir.

Coolant is towards the center under the cover. And yes you’ll need a gallon of coolant if it’s low.

 

ah ok thanks Doublebase, I just found this information online and tried to delete my post but too late with your reply

thank you, looks like I need to buy some coolent

 

The coolant reservoir is on the passenger side of the car, up front next to the radiator; if I recall correctly. There is an inspection hole in the engine compartment panels, that allow you to view and add coolant without removing the panel. There is a full and add line on the tank that will provide you with a target level.
There are several different kinds of coolant, and they should not be mixed. Toyota coolant is a red/pink color. You would be okay to add some distilled water to top it off, but it may compromise your antifreeze properties and anti corrosion value. The reality is, if you’re low on coolant, you have a leak. I would top it off with distilled water to the full line on the tank, and get it to a mechanic to find the leak. Part of the repair should be coolant replacement, as that is a regular maintenance item. Even if you don’t live in a climate where coolant freezing is a concern, you want to make sure your coolant is fresh because of anti corrosion and coolant system lubricant. When I got my 2007 LS460 with 80,000 miles it had a slow leak from the water pump, and I was loosing coolant.
Good Luck!