First, read the English article below.

Click the down arrow button in the top-right corner of the Firefox window. This will display your recent downloads. Clicking on a file in the list will open it (if it still exists). Clicking on the folder icon next to the file will open the folder with that particular file selected. In the Recent Downloads list, click "Show All Downloads". This will open the Firefox Library, with the Downloads tab selected. All of your stored downloads will be shown here. You can use the search bar to find something specific. Click the Firefox Menu button (☰) and select Options. Click the "General" tab. You can change the folder that your downloads are saved to by clicking Browse... You can also choose whether Firefox should prompt you to save a file when downloading. 

Now, please write a short abstract for it in Vietnamese. Abstract:
Mở danh sách Recent Downloads (Tải xuống gần đây). Mở Downloads Library (Thư viện tải xuống). Thay đổi thư mục Firefox Download.