Against a wall or fence on which you can put a support, in the sunniest, warmest spot you can find - south facing wall is ideal. They're said to produce more fruit if the roots are constricted, so some people do this by constructing something in the soil 18 x 18 x 18 (with bricks or something) and then planting in the middle of it. This assumes you mean Ficus carica, the outdoor fruiting fig, and not the houseplant type, such as Ficus benjamina.