You can dissolve the primers with 100 ul of 10 mMTrisHCl, pH 8 or TE. This will give you a stock solution of 100 pmoles/ul. For PCR use, you can further dilute the stock 1:10 to give a 10 pmoles/ul working solution. Use 1 ul of the working solution for a volume of 50 ul PCR mix.
one additional side note to what creativeproteomics has touched on-
I preferred to prepare the working solution of primers with ddH2O. Since the DNA polymerase reaction is Mg-dependent, by doing the 1/10 dilution with ddH2O can ensure the amount of EDTA in the final PCR reaction become insignificant.