To locate your comic(s) use the search feature at the top of the page. When searching for a title search for a portion of the title. For instance if your title is "The Amazing Spider-Man", try searching for just "am spid". Locate the series in question and after clicking on the title you will see a list of issues for that title. Find your book by the number and either add to your collection, or just use the price as a reference.
You can also visit the guide page at http://comicbookrealm.com/guide for further instructions.
Please be aware that we get a lot of questions about this issue and this is just a canned response. If you would like more help please use the forums and a member will be glad to help you.