One 7-segment display is making a cameo appearance in the Bela Kickstarter video
The code for that is long gone, but it is fairly straightforward to drive it directly from the Bela digital outputs: simply connect each digital output to one of the LED pins of the display (through a suitable resistor (220ohm?), unless one is built into the display), and connect the COM of the display to the ground of Bela. The code would then just use
digitalWrite() to turn on the LEDs in turns.
If you want to use fewer digital pins and/or you need to drive more than 2x 7-segment chars, you may consider using a shift register instead, so you could drive an arbitrary number of segments only using 3 digital pins from Bela. I see that some LED displays come with a TM1637 driver, which offers some extra capabilities (e.g.: brightness control) ... that's yet another option!