Have a read through the tar man page for starters
Man Page for tar (Linux Section 1) - The UNIX and Linux Forums
Tar is one of the most difficult commands to master (IMHO) as it's command line syntax is very "old school". There are a fair few options to deal with, but to create a simple tar file of the current directory you only need to pay attention to the create "function letter," the file (archive) name option, and remember that dot (".") represents the current directory.
The examples in the man page, and these few hints should get you going.
If you have specific problems after you formulate your command, post those and someone will be happy to help.