Open the movie poster you are working on in your graphic design program, such as Adobe Photoshop, GIMP or Pixelmator.
Click the "Text Tool" button on the tool bar of the graphic design program.
Select a condensed, sans serif font, such as Futura Condensed, Univers Thin Ultra Condensed or Tall Skinny Condensed.
Choose a color for the font that will complement the overall design of the poster and be clearly visible. For example, a white font should be used on a dark background. Select "Center" for the alignment of the credit billing block. Center-aligned credits are typically standard for movie posters, but using a left or right alignment is appropriate if it better fits your design.
Left click at the top left corner where you want to place the credit billing block and drag the cursor to the bottom right corner of where you want to place the block. A text block will be created.
Type the credits you want on the movie poster's billing block. Always put production company credits first, before the title of the movie. If you run out of room for the credits, highlight all the text you have entered and make the font size smaller by using the "Character" editor from the text tool.
Add production company logos to the bottom of the billing block, when finished. An MPAA rating can also be added, as long as the movie has actually been rated.