How do I start at the start and work my way to the end?

Easy. Consider yourself you don't know literally anything. Go to the first course on Courses and click the one that is on the top left. If you see the content easy enough go to the Unit Test and do it. Aim for the 100%. You will see that sometimes is better to the section test instead of the unit test, to be more effective in terms of getting the 100%; you will see it when you practice. The key is to work. You see is to easy, aim the 100% and move on. You see is too difficult, go one step back and get the 100%. Good luck. 

Pablo while I appreciate you taking the time to answer, I feel like you’re replying only to the subject heading without reading my full question.

According to your approach, I would be doing Arithmetic after 8th grade which makes no sense.

Also I would be doing Algebra 2 before “Getting ready for 3rd grade”.

Also I’d be covering the same material multiple multiple times.

Would you please re-read my question and see if your answer changes?

Hello Sverre. Yes, I agree the Arithmetic one is not the best course to follow after 8th grade. Luckily, you will obtain a great amount of points from that course if you have finished the previous courses with a 100%. 

Basing myself on our short interaction I would suggest you starting on Algebra 1. You said you forgot how to do Long Division and that topic corresponds to Algebra 2. I made you that suggestion because then you talk about 2nd grade math which is clearly on another level.

Start doing Freshman high-school stuff and if you feel you don't understand go back to 8th grade. 

Do 100% on this courses in this order:

Algebra I -> Geometry -> Algebra II -> Trigonometry -> Precalculus -> Calculus AB -> Calculus BC -> Multivariable Calculus -> Differential Equations

You can do Linear Algebra at the end or after Calculus BC.

In my opinion is not that important where you start and the strategy you follow, but to start working. See where you have gaps and correction.

The problem with your question is that is not clear at what level you are. Algebra II is a significant different level than 3rd grade as you might expect. Also in my case the Get Ready courses are after the Middle-school courses. Luckily for you, if you do the 100% on say 5th grade, you also have the 100% Get Ready for 6th Grade course. 

If you have any suggestion or concern, I'll try to help. 

Regards,

Pablo.

Thanks Pablo, I appreciate your advice on what courses I should do.

But I don't think you're correct saying that I don't know what level I am, because as I said in my initial question, I want to go right back to the start. 1+1=2 and work my way forward. My level is "someone who has never studied math in their life".

So I guess my question is this: Is there a standard course order WITHIN the Khan Academy software itself, and if so, how do I see it?

There is no standard course-path offered by KA itself.

However, I don't see much difficulty in setting it by ourselves, specially because you are saying you want to start from the very beginning.

Do this: 

1st grade -> 2nd grade -> 3rd grade -> 4th grade -> 5th grade -> 6th grade -> 7th grade -> 8th grade.

1st grade is a good start for someone who wants to start from 0.