There is a search function reached by tapping / clicking on the magnifying glass on the right if the blue bar under the CC banner. Functionality is slightly different depending on the device being used and in the case of some mobile devices, the orientation.
On a PC or wide screen mobile (landscape usually), navigate to the roll call then type the search criteria in the search bubble press enter. (As you type the words This Topic will appear on the right.) If you are looking for a particular phrase enclose it in quotes, e.g. "Royal Princess". Otherwise the search will return every post that contains any word in the search bubble.
To search particular forum navigate to the forum and type in the search criteria. The search will default to This Forum.
There are many more options and methods but this should get you started. At least enough to find the topics in this forum talking about search.