Is there any Tool that can be used to calculate frequency (MAF) by using rs ids of snps?
MAF in your cohort (VCF)? Otherwise, you can use EXAC database or dbSNPs.
Can you provide with me guideline that how can I use dbSNPs or EXAC Database?
Yes, I recommend trying Variant Effect Predictor because you can get frequency broken out by subpopulation. Link is here:
Can submit one or a list of rsids.