Assuming is planted outside, remember it's only hardy in the UK if given protection against frost during the winter months. The hardiest seems to be the Japanese, Musa basjoo.
1,Cut all the leaves off as they begin to turn yellow around october.
2, Erect some kind of structure around the stem/s using old wooden pallets, fence pailings etc, leaving plenty of room from the plant.
3, Pack the structure with straw (fluffed up) to provide good insolation.
4, Now you need to cover the plant with a secure cover to keep out the rain which could cause it to rot. Use a tarpauling or sheet of roofing felt.
When all signs of frost have gone usually mid-late may, take off the covers and hopefully fresh green leaves will start to unfoil.
If you are lucky enough to get it to flower,that stem will then die and may as well be removed to make way for new stems, it may take several years before flowering as mine did.
They are hungry plants and will reward you well for adding plenty of well rotted farm yard manure, treat it like rhubarb with lots of horse dung! and you should get leaves 6' +
Good Luck Tbird+