Dear Neelima,
The best thing is to search on Google with the keyword "Free Excel Guide or tutorial." You will need at least a month or more to go through what you get. Neelima, it's good if you become more specific on what you need in Excel immediately so experts can guide you on them. Do mention which version of Excel you are using in your query to avoid confusion.
I have been using Excel for the last 10 years, and I still have so much to learn. I have experienced that Excel can be best learned with examples and practical tasks. Take it from me.
All the best.
Ukmitra