Good Morning

I am very new to crochet and would greatly appreciate any help with respect to joining granny squares. Regards the link below, I cannot understand how to join the first two squares. The video at the 6 min 35 sec point relies on the gap between the two squares above, which are already joined. Therefore, how do you join the very first two?

The point I am stuck on is after crocheting the border around the first square, followed by crocheting the border half way along the square to be a joined to it and having completed the three trebles and one chain stitch in the corner - how do I join it to the first square? The video at 6 minutes 19 seconds through to 6mins 42 seconds demonstrates how to do this when connecting the square to a row of squares above but the instruction at 6 minutes 29 seconds to 6 minutes 32 seconds shows the needle is inserted into the gap created by the joining of the two squares above (6min 29 second mark). This gap obviously isn’t there when you join the first two squares together and I cannot fathom where to put the needle for the first time in the first square when joining the second.

Any assistance gratefully received

Jacqui