To create a table in Word, choose Table from the Insert tab. Word will display the Insert Table pop_up. Use your mouse to select the number of columns and rows in your table. As you highlight the row and table combinations, Word will display the corresponding table in the document below the Insert Table pop_up. When you have highlighted the number of rows and columns you need, click the mouse button. Word will insert the corresponding table into the document. You can adjust the column widths and row heights as needed. Additionally, when you insert content into a cell, the cell width and height will adjust accordingly.
You can look online for sample proposals that you can work from, in many cases you will be able to download a template that you can work from. You will most likely find that there are dozens of sites offering hundreds of different templates to download. It may take a while, but you will find that there proposal forms that will match almost any need including yours. Take your time and select the one that best suits your needs.