First of all for using data plan in Nepal Telecom you should activate the data service in your sim card. You can do this by following the steps after you dial 1415 or else you can contact the customer support and they shall activate the data plan on your sim card. In next step check if your data mode is on in your mobile device, just set the APN to the default and you should be good to go. If it does not work again then just contact customer care and ask for them to send the install package for your device for 3G or 4G.
Hope it helped you.
