Hi @liangy10
Usage is Galaxy is generally the same as the command-line version of tools for file formats. The Help section on tool forms try to clarify anything “Galaxy specific” eg what datatype to give the inputs.
These tutorials have example data (initial + computed) along with methods (hands-on + workflows). Navigate by analysis domain or search with keywords like tool names.
The GTN is hosting a training event all next week. GTN materials will be included with live support from scientists from around the globe who work with Galaxy. 
Smörgåsbord 3: A week of Free, Online, Galaxy Training supported by the Global Galaxy Training Community