Imputing allele frequency into GWAS summary statistics

Question

[newbie problems]

I have a summary statistic file which has the the following columns

Column Description ID_37 Variant ID (GRCh37) Chromosome Chromosome number Position_b37 Position GRCh37 Other_allele Reference allele Effect_allele Effect allele Beta Beta associated with effect allele SE Standard error P-value P-value

How can i add another column for the frequency of the effect allele? Thanks