In the affiliate panel at Promotion > Advanced tools > Signup subaffiliates
there is a section called "Download Our Signup & Login Form"
If you wish to hide that section then you will have to follow the steps below:
1) in the merchant panel at "Configuration > Design > Affiliate panel theme" click 'Edit them' on the currently active theme (in case a dialog pops up claiming to create a new theme, then read here
) and look up the following file:
2) In the above mentioned file you will have to remove (or comment) the block of code highlighted in the screenshot below:
Do not forget to click Save after removing (commenting) the mentioned code.
Now, if you go back to the affiliate panel (do not forget to refresh that page) there will be no "Download Our Signup & Login Form" at Promotion > Advanced tools > Signup subaffiliates