I assume you mean Kilmarnock Willow - won't do well contained in a pot for any length of time, so aim to plant it in the garden with in 2 years. Give it a pot big enough and repot as soon as it needs it, keep well watered during dry spells, particularly as its in a pot, you'll need to water regularly anyway, feed by adding Growmore granules or similar once in Spring and again midsummer, although if you pot it up in fresh compost, it won't need feeding for six weeks. Keep an eye out for rust infection - these plants are prone to this.

thanks for your time to answer.