PETSc is a sophisticated package; and fully understanding its usage requires time. However, application programmers can easily begin to use PETSc from a high level, and then gradually learn more details according to their needs. Users should read the users manual before attempting to do any serious coding with PETSc!
PETSc Manual Pages AMS manual pages MPI manual pages TAO manual pages
The manual pages are split into four categories; we recommend that you begin with basic functionality and then gradually explore more sophisticated library features.