The following example is based on trading one standard lot on WTI Crude Oil:
Position Size: 1 standard lot
Contract Size: 1000 barrels
Contract Value: $10 per point
Margin Requirement: 1%
Total Exposure: 41.58 * 1000 = 41,580 USD
Margin: 1% * $41,580 = $415.80 USD^
^You will need to convert the margin amount into your base currency if it is different to the currency of the index your position is opened.