It is not possible to install the Kobo software. If you don't like Tolino Reader, the solution is the one discussed by @ottischwenk: access Android and install alternative reading software. In my opinion, AlReader and KOReader work very well on the Tolino, much better than the native reader program.
On this German forum there are clear and detailed instructions on how to access Android and install alternative software. It is very simple.
https://forum.alles-ebook.de/thread/...d-anwendungen/
Edited: (It is convenient to read the whole forum, although in these two links everything is more condensed)
- Explained in images (with link to the necessary files)...
https://forum.alles-ebook.de/thread/...7411#post87411
- A good summary, step by step...
https://forum.alles-ebook.de/thread/...7642#post87642