It will be a great help if someone could share a content/tutorial about how to design the coefficients of Wide-band FIR Filters.
As it stands your question appears to be quite broad, so the answer depends largely on your application and level of knowledge.
If you have no prior experience, you might want to consider picking up a book about digital signal processing, e.g.
which may be available in your local library.
For digital filters specifically, there are great resources available online such as this free book:
There is also the Cookbook for audio EQ biquad filters by RBJ which you should also check out, found for example here (although i cannot find the original link right now).