You can make a poster on Google Docs by following these steps:
1. Open a new Google Docs document.
2. Click on "File" in the top left corner of the screen, then select "Page setup".
3. In the "Page setup" window, choose "Custom" from the dropdown menu for the paper size.
4. Enter the dimensions of your poster in inches, such as 24" x 36", and click "OK" to apply the new size.
5. You may want to adjust the margins to zero to maximize the space available for your poster.
6. To add text or images to your poster, use the text box or image icon in the toolbar to insert and edit the content.
7. You can also customize the font, color, size, and alignment of your text using the toolbar.
8. Use the "Arrange" menu to adjust the position, layering, and grouping of your text and images.
9. To add visual interest to your poster, try using shapes, lines, and other graphics from the "Insert" menu.
10. Once you are satisfied with your poster, you can print it or save it as a PDF.
That's it! With these steps, you should be able to create a poster in Google Docs.