在main.js :

import ElementPlus from 'element-plus';
import 'element-plus/theme-chalk/index.css';
import 'element-plus/dist/index.css'
// import locale from 'element-plus/lib/locale/lang/zh-cn'

將 createApp(App).mount('#app') 替換為：
createApp(App).use(ElementPlus, { locale }).mount('#app') 或
createApp(App).use(ElementPlus).mount('#app')

即可在.vue中直接使用：

import { ElMessage } from "element-plus";
...
ElMessage.info(info);