You can set your service to 'ScorchedEarth_P' map by doing the following steps -
1. Navigate to the Commandline Manager in TCAdmin and open it.
2. Select the Custom Commandlines tab and create a new commandline (you don't need to create a new commandline if you have already created one).
3. You should then see a list of parameters that you can set, locate the 'Map ID' parameter and tick the checkbox next to it, then change it from TheIsland to ScorchedEarth_P.
4. Simply scroll down to the Save button and then save it, once you have done that simply click on 'Select' and then start your server.