AusBonsai

Funnily enough after having a quick look on Google I just realised I already have one of these which I bought as a Himalayan Cedar That one has the same problem with leggy branches, although it had enough lower branches to train down and trim back a bit so I've managed to get it into a nice shape and am just letting it grow for now.
This one is far too tall, I think, for suitable bonsai material. An impulse buy which was looking a bit sorry for itself hidden behind some black pines so I bought it and then wondered what the heck to do with it. It does have a nice trunk but all those weird leggy branches at the top.
I'm considering just putting it in a large pot and trying to thicken the top foliage and let it weep. Any tips on this one? Or some pruning advice to get the top a bit thicker?

Olga,
Cedars are slow to develop. The only way I know to get the branches more dense is to prune back long bits and pinch all shoots to promote budding. You can cut and pinch shoots back to leave just a few needles and buds should grow most times on healthy trees. It will take quite a few years of constant effort.
Before you try this I think you need to get the tree healthy. Feed it lots and probably repot to encourage growth then cut back later.

Ah yes I was deciding whether or not to repot it or pop it in the ground, the other small one with the bluish foliage is in a grow patch at the back of the garden the moment. Thanks Shibui, do you have any advice on fertilizer? I'm still investigating different ones.

Any fert is better than no fert. Use anything you have available but follow the directions on the packet for safety.