The sound card should have some information from the manufacturer about sending data to the individual channels. If not at a hardware level (which registers to address), then how to send it through the driver for the card.
The output is from a digital to analog converter. if 16 bit, then the magnitude of the sound will be dependant on a value of 0 to 65767 decimal. Do some reading on the sunbect of d to a converters for an answer to the frequency question. You will be making a file of numeric values that will be sent to the sound card. The contents of the file will control the output in frequency and anplitude.
If I interpret your question about time as distinct from frequency, the intervals between your non-zero values will control the timing between outputs. - or you can send the smame file over and over, with intervals between the transmissions to establish timing periods.