Apart from "one" that has three different variants in Russian (ОДИН / ОДНА / ОДНО), "two" is also not as easy as one-two-three! It has two variants too: ДВА / ДВЕ. When to use which? Well, you need to think about genders when you are trying to choose: masculine and neuter nouns would go with ДВА and feminine – with ДВЕ. But don't forget to change the noun you are using into a Genitive case (singular), because that's the rule:

1 + Nominative singular

2-4 + Genitive singular and

5-20 + Genitive plural.

ОДИН СТОЛ —> ДВА СТОЛА

ОДНО ОКНО —> ДВА ОКНА

ОДНА СУМКА —> ДВЕ СУМКИ

No worries, other numbers always stay the same: три, четыре, пять, etc. They do not change according to the genders of the nouns you are counting. Just be patient and remember ОДИН / ОДНА / ОДНО and ДВА / ДВЕ!