I'm not sure where you could find informative pamphlets concerning 3-5 year olds, but I have located a couple of sites that may have the information that you are looking for, links below.
If you prefer having something that you can hold in your hand, you may want to subscribe to a magazine. Parenting & Family Fun are two great ones that have lots of fun ideas, recipes and great articles concerning our little ones' milestones and development issues, links below.
Also, Education.com has many articles, worksheets and activities that you may be helpful.
If you can be more specific about what areas that you are having difficulty understanding, maybe we could be more helpful here on education.com, but remember, no child came with an instruction manual and as parents we know our children's needs best.
Hope this was helpful and just click to "add to question" to give more details on what it is you're searching for, we will gladly help by sharing our personal experiences. Whatever you're facing, rest assured that at least one of us have been there too.