I must mention that guidelines differ from country to country. In South Africa, there is also quite a difference in practice between the public and private sector, largely due to resource availability.
In South Africa, women should start pap smears at the age of 25, or at time of diagnosis of HIV -seropositive. If HIV negative, get a Pap smear at least every 3 years and if HIV-positive at-least once a year.
NB: this is assuming high resource areas, and that the previous results are negative
Top-Tip:
ASK your gynae to thoroughly explain what your results mean.