Once you’ve made the required length of chain, you should be left with something looking like this. This is your foundation row, into which Row 1 is worked.
The starting chain instructions often include the turning chain in them already. This example shows a treble crochet, so the stitch is worked into the 4th chain from the hook to create the height needed for the first stitch.
This is what the first treble stitch into a chain looks like – you will then continue to make the next stitch in the next chain all along to the end to create your first row.