Texts of image attached in above suggested clearly that:
1. You have entering into page (192.168.0.102:9090),
2. The server is uTorrent and
3. It asks for User Name and Password
4. Youtr D-Link port forwarding (9090) is correctlty defined
The user name and password requested here (http://192.168.0.102:9090/gui/) is the BitTorrent admin name and password.
It is different from the name and password you have used to access Navigator (http://192.168.0.102/static/root.html#).
If you have not changed the BitTorrent user name and password, then, you can use the default as in below:
user name = admin
password = "blank" or just hit Enter (i.e. no password)
You may refer to page 116 of LinkStation User Manual for detail.
I would suggest you performing below before your next attempt
1. Disbale BiTorrent
2. Enable BitTorrent
3. Run (click) "Initialize BitTorrent Settings"
Hope this is helpful.
Goofd luck...
--JC