To say what you want there are two expression in Chinese:
想 (xiǎng) is used in the sense of 'I would like'.
e.g. 我想喝一杯咖啡。 - I would like a cup of coffee.
Note: 想 has a range of other meanings, for example to think, to feel or to miss.
要 (yào) is stronger then 想, it is used in the sense of 'I want'.
e.g. 我要去北京。 I want to go to Beijing.
Like 想, 要 also has other meanings like 'shall, will, be about to'.