Manual here
Unfortunately, as they stand, these items are fundamentally incompatible, and cannot be connected together.
The HWT150 only has a digital output and your TV only has analogue inputs.
Obviously the ideal solution would be a new TV too, which would allow you to gain all the benefits of High Definition television that this box can offer, but I appreciate that is a significant expense which you may not want at this time.
A 'workaround' is to get a small HDMI to Scart converter box such as
this for example, which would allow you to connect the two together.
You would require an HDMI lead to connect the '150 box to the converter, and a scart lead to connect from the converter to the TV.
If you decide to take this approach, be very aware that a
HDMI to Scart converter box is very different compared to a
Scart to HDMI converter box.
Despite having identical connections, they have completely different functions.
You require the former. i.e. a HDMI input to Scart output converter box.