It's important to establish which variety of bamboo it is - if its made five feet in a pot, then bear in mind some varieties can get upwards of 20 feet, and many types are highly invasive at the root, spreading outwards aggressively unless restrained by a root rhizome barrier. If yours is a running type, you risk it popping up several feet away.... As for pruning, its not usual to prune them at all, unless you want to cut out any dead canes, or remove leaves to reveal more of the caulms or stems.

It would help to know what your definition of too "bushy" is, Chega. Is it too dense--not like a Japanese watercolor--or too wide or tall?
If the former, You can thin out the thinner and older canes, cutting as close to ground level as possible. Those can be dried for indoor decoration, or flower stakes. Sometimes, it may be necessary to thin out some of the lower foliage branches, and a few middle level ones, to provide sight lines to the canes.
If the latter, you can cut the longest canes back to side branches, preferably to within the new outline of the plant. Until new growth develops, it may look a little clumsy with "squared off" cane tips.
Now might be a good time to prune, since new growth will be appearing soon, though you might want to wait a few weeks in your cooler climate. Some adjustments might be necessary once the new growth develops some maturity. Normally, I would not remove more than 1/4 of the foliage at a pruning session.

Thank you for your replies,the lady who gave it me already had another more upright one and only a small garden, its seems to have settled in a more upright appearance now the growth heading more up than width ways, by bushy the stalks appeared to spread out to 3ft now look more compact,will give a trim and although its in a paved area(one paver taken out to replant) I will watch out for spread

Bamboo sprouts have been known to lift up pavers and crack concrete, as they grow. I wouldn't rely on paving to contain it. As for trimming it, I would selectively prune it, rather than taking out the hedge shears.

Thanks for the point about lifting paving,will watch out for that Tugbrethil,yeh last thing I want is to haircut it ,want it to look natural as possible,seems to have taken slight sign of settling bit of new growth