Deepti,here are the commands that can help you..
file name is x--

1.. vi x --> file is open in commad mode.
2.. for navigation in vi use these commands-
a. h->to move left
b. j->to move down
c. k-> to move up
d. l-> to go right

3.. To write something in vi you have to press i or a to put u in insert mode or append mode.write something in file.

4.. press x to delete a word,dd to delete a line,r to replace a word.
5.. see man vi ->there are so m any commands to do editing and navigation.
6.. To save press escape :wq ->it will save and exit.
escape :w ->only save
escape :q quit
escape :q! ->quit without save.

Thanks,
Namish