Drafting IEC publications
(The full requirements are given in the ISO/IEC Directives, Part 2, clause 6.6.5 Figures.)
Give each figure the designation "Figure n", where n is an Arabic numeral starting at 1. In annexes, the numeral follows the letter designating the annex and a full stop (e.g. Figure A.1).
To deal with figure numbering in the most efficient way, see Creating captions for figures and tables.
Place the caption below the figure, and apply the style Figure caption from the IEC standard template.
Please also read the instructions on dealing with text in figures.