Historical Abstracts is an EBSCOhost database, so check out some of the Academic Search Elite Search Tips - they will apply here too!
Get friendly with UI Link - you'll need it! Most of the records within Historical Abstracts contain citation information and abstracts only. Use UI Link to find the full text of a promising article through the other databases the library has access to.
Clicking UI Link will show you other databases that have the full text of the article you are looking for. If none of UI's databases contain the full text, click "Request this article by Inter Library Loan/Document Delivery" at the bottom: this will link you to the ILL request form, and should have all of the fields filled out for you! (You will need to make an ILL account if you do not have one already.)
Want to search for world and American history at the same time? Select multiple databases to search! Directly above the search box, you will notice a blue "Choose Databases" option.
Click that, and a list of all the EBSCOhost databases the University of Iowa's Libraries subscribe to will pop up. Scroll through until you find "America: History & Life," a good database of North American history, or any other database you would like to search. You can select as many databases as you want! Do note, however, that this may increase the time it takes for your search to pull up results.
Because Historical Abstracts covers world history topics, you will likely get results in other languages. If you want those, great! If you don't, you can limit your results to English with the menu on the left side of your results list. It will likely be at the bottom of the left-side menus.