Adding text in Fotophire is rather easy too. Once you’ve opened your image in the Photo Editor, head to top right side of the interface and click the large “A” button. Select the desired font and click on the area where you want to add text. Write the text in the textbox. All ...
The font used in the screenshots is Andale Mono (don't ask why, it just is). The font size is 10pt. If you can't get Andale Mono font (I think it might be a non-free MS core font), use an existing font that looks similar. The contents of the file in the screenshot are a...
To gauge the appropriate size, use 175 pt font on the artwork. When this gets added to the actual silkscreen the size will be around a 1/4" high. You can experiment with the size depending on how much room your logo or artwork needs to take up vs. the size allotment on your PCB....