can i make my icons bigger on iphone 5?

No but if you press and hold your finger down on an empty spot on the screen a magnifying glass will appear that you can use to look at things a bit bigger.

Settings>General>Accessibility>Large Text.

Also, you can turn Zoom on on that same settings page. Read here:

http://support.apple.com/kb/HT3577

You cannot enlarge iPhone icons. There is no option to do that.

OP wants to have larger icon not larger text.

Large text do not make icons larger.

Try

'settings>general>accessiblity>increase contrast'

to better the legibility before solution comes out in the future.