Posted: 12/08/2015 at 13:59
Multi-blue is a group 2 for pruning which means it gets a light trim after the first flush of flowers in late spring, early summer.
However, I think the main problem with yours is thirst and hunger. It looks very dry and, in its first year, won't have had time to send its roots down deep looking for nutrients and moisture. Clematis are very hungry, thirsty plants so I suggest you start by giving it a generous drink - at least 5 litres - or diluted tomato food. Repeat after a few days and until the autumn rains set in in September. Then you can give it a generous mulch of well rotted garden compost or manure and leave it till spring.
In spring, give it a generous feed of proper clematis food and cut back all stems to a healthy pair of buds. Give it some more trellis either side of the existing panel as it will want to spread and training its stems horizontally or diagonally will encourage extra flowers. Feed it with weekly drinks of tomato food. When the first flush of flowers is over in June, dead head them and keep up the feeding and you should get a second flush in late summer.