What kernel version are using? Have you load the overlay 'BB-SPIDEV0' to the cape manager? You should see something like /dev/spidev*.* after the SPI is enable.
If you are using kernel version larger than 4.4, then you just configure the pin to spi mode using 'sudo config-pin PIN_NUMBER spi', for do, di, cs and sclk.
For a lower kernel version, just load the related overlay under /lib/firmware/