F-test is used for testing equality of 2 population variances.So your hypothesis is (2tailed)
Ho:- their variances are equal v/s H1: not Ho
In this case your , Ho is retained it means the variances are equal i.e. the samples are drawn from normal populations with same/common variance.
Since , we have verified the assumption of common variance using F-test , we use pooled estimate for independent samples t-test(comparing means).
Hope this answers your doubt.