If you are referring to TXWARN, the most commonly used system in the Houston Metro area, you need to monitor specific sites, not only certain conventional frequencies. You would import the site nearest you, being sure that you import the correct site for your agencies of interest. All talkgroups are not carried on all sites.
For your WS1065, you could load the frequencies for more than one site into one TSYS object, up to a max of 32 frequencies total. Than set the object to Stat and 'check all control channels' so that it would,, in effect, scan all the sites each pass though. For the 996P2, you import the sites separately, not combining frequencies from other sites into the same one. The Uniden scanners will find and use the first active control channel encountered in the list, and keep going back to that frequency even if reception on another programmed channel was better. So, import the site(s) near you, that carry the agencies you want to hear. Import each site as is; don't add other frequencies from a different site into the list.