Dear Irina,
regarding your questions:
1). The new version of the theme should be available form your ThemeForest account, the “Downloads” tab. You’ll need to download it, unpack as stated in the manual, and re-upload the “Sensei” folder (located inside the “Sensei_Installable.zip” archive) via FTP, replacing the original theme files.
2). The reason why there were no widgets in the default sidebar is because you did not add any :) widgets can be added in “Appearance -> Widgets” by dragging the widget boxes into one of the sidebars on the right. I’ve added a couple of test widgets to your default sidebar and they show correctly, please see e.g. this page. Now the second part of the issue, i.e. the custom sidebars, is still open (although you had no widgets in them – even after adding widgets they did not work) – I strongly recommend to try to update the theme to the latest version and check if it fixes the custom sidebars. If not, please let me know!
3). The fancybox is working fine at the moment, just click on any image you’ve inserted into posts or pages, e.g. this one. Note that in WordPress an image must be inserted with a link pointing to the image file in order for the system to create a fancybox frame for it.
Sincerely,
Andrew | Satori
P.S. с наступающим! ;)