When you first complete your purchase, you will be directed to a link where you can download your fonts.
You can also access these from your account at any time, in the 'Order history & downloads' section.
To find your account you click on the person icon on the top right hand of every page, the icon is shown below:
Once you are in your account, you will see a section like the one in blue below, on the righthand side, you can see 'Order history & downloads' at the top
If you select 'Order history & downloads then you will be taken to a screen like the one below, were you can download your purchased fonts: