Ooookay!
Let's go!

Now, you see how the shape we have could be like a triangle on top of a rectangle? Well, you wanna take that triangle and fold it down. (Red lines towards blue lines)

It should look like that

For the next step there's not really a correct measurement, it's just folding the bottom so that it covers the cusp of the triangle.

(You gotta finish the fold, I just forgot to take the picture before doing the next step and this is the closest to the result) but yeah, more or less that measure.

Next step is basically unfolding the the last fold and the triangle and refolding it so that the triangle ends on top of the 'rectangle'

Should end up looking like that.

Now you have to fold one half so that the bottom side (red corner) ends in the middle (where the cust of the triangle is, blue line)

Result^

Now you repeat the same but on the other side

Once again, next part can be a bit tricky if I don't explain it clearly enough, so I hope it's clear enough.

We're gonna zoom on that part for the next step

As you can see, there's a "hole" or cavity in there.

So the red corner should co inside there, by folding just as we did on the last step but tugging it in there.

(Idk if the image is clear enough to help, but it's basically that)

It should look like that

Now we have to do the same on the other side

Reeeeeeesult^

(Hopefully that was understandable)