The keywords list in AntConc is, as the name suggests, a tool to create a list of keywords. To do this your target corpus is compared to a reference corpus. The target and reference corpora do not need to be of the same size. The comparison is then done statistically. The statistics in AntConc used for this task are either chi-squared and log-likelihood.
In AntConc load your corpus or corpora. Go to Wordlist tab then click start.