It's a green icon with a white "X" on it. The Microsoft Excel home page will open. Type invoice into the search bar at the top of the page, then press ↵ Enter to search for invoice templates. You must be connected to the Internet in order to search for templates. Click a template that you want to use to open it in a window. This button is to the right of the template's preview. Doing so will open the template in Microsoft Excel. For example, most templates have "Company" written across the top; you would replace this heading with your company's name. To edit text on the Excel document, double-click the text item, then remove the text item or replace it with your own. Enter any information required by your invoice template to ensure that the final total matches what you're owed.  For example, some invoice templates will require you to enter an hourly rate or a fixed charge. Most invoice templates use formulas to combine your entered hourly and the number of hours worked in the "Final Total" box. Click File in the upper-left side of the page, click Save As, double-click a save location, enter your invoice's name, and click Save. This will save your customized invoice in your selected save location. Your invoice is now ready to be sent.

TL;DR in Vietnamese:
Mở Microsoft Excel. Tìm mẫu hóa đơn. Chọn mẫu. Nhấp vào nút Create (Tạo) nằm bên phải bản xem trước của mẫu. Chỉnh sửa mẫu cho phù hợp với nhu cầu. Điền vào hóa đơn. Lưu hóa đơn.