Welcome to TeX.SE. Sorry that we can't really help without more information. The best way to provide that is by way of a MWE including \documentclass and the appropriate packages that sets up the problem. If you are drawing on an existing image see the link that @Werner linked to. If you are doing the figure in LaTeX you add math text the same way you add math to normal text in that you with a pair of $ (or a \( and \)) . If you provide a MWE you can get a more detailed answer.
– Peter GrillApr 02 '14 at 23:50
psfrag? – Memming Apr 02 '14 at 22:37\documentclassand the appropriate packages that sets up the problem. If you are drawing on an existing image see the link that @Werner linked to. If you are doing the figure in LaTeX you add math text the same way you add math to normal text in that you with a pair of$(or a\(and\)) . If you provide a MWE you can get a more detailed answer. – Peter Grill Apr 02 '14 at 23:50