If you know a command name but want to check the syntax, type the beginning of the command name, then the tab key. This will display the command index, with the current position at the first command after the command name beginning. You get a short description and a few examples displayed. Left-clicking on an example should complete the command line with this example. Right-clicking will fill up the arguments inputlines with the example, so that you can modify some of these arguments before clicking OK. You can get a more detailed help inside your browser by clicking on the Details button (this works for most but not all commands).
If you don’t know a command name, you might find it using the menus or browsing the table of contents of the CAS manual. If you know the TI89/TI Nspire CAS or the Maple language, you can also try their command names.