How do I create a folder in Gmail to organise my inbox? I only see 'labels'.

In Gmail, labels ARE folders, just more flexible. To make one: on the left sidebar scroll down and click 'More' > 'Create new label' (or the + next to Labels), name it, and it appears in the sidebar like a folder. Drag emails onto it, or open an email and click the label icon to file it. The twist versus real folders: one email can carry multiple labels at once (say 'Work' and 'Receipts'), and applying a label doesn't remove the email from your inbox unless you also Archive it. So the proper 'file it away' move is: apply the label, then archive. You can colour-code labels too, which makes the inbox much easier to scan.

Labels do everything folders do and more, one email can sit under several. The bit that trips people up: labelling doesn't move it out of the inbox, you have to archive it too for a true 'filed away' feel.