Right now, predictions are 4-5 million refugees to come from Ukraine to Europe and other parts of the world - women and children, and those over the age of 60, as all men between 18-60 must stay in Ukraine to aid in the defense. The humanitarian crisis is something not seen since world war II in Europe. The most will come to Poland, Slovakia, Moldavia, Romania and Hungary, the neighboring countries. The whole of Europe is opening their borders unconditionally, and the EU is going to give all the aid they can to the neighboring countries of Ukraine.
But, if you want to and can help, there are always the large international aid organisations to support, for example the Red Cross, or UNHCR. They do very important work in the areas and in Ukraine.