The Thursday night events are also type-B time trials (club events) so all you need to do is to turn up around 20-minutes prior to the start time.
The second results column is explained as follows:
All riders over the age of 40 are classed as veterans and is assigned a 'standard time' for the event, dependent on distance, machine and gender. Think of this as your target time.
The plus result is based on the difference between your actual time and your standard time. If you a quicker than your standard the 'plus' will be positive and if your time is slower than your standard it will be negative.
In your case, you were 7'58" slower than your standard for this event.