First of all you need to design your layout in some way where the journaling will be placed on a strip of paper 8 1/2 x 12 or smaller. I format my word document to legal sized paper and landscape. I then type my journaling in a text box and move it to where I want it to be printed. Keep in mind that legal size is 14 inches long but your scrapbook page is only 12 inches so be careful where you place it! I tape 2 sheets of printer paper together to get the longer length I need and print my journaling.
Next I cut my background cardstock to 8 1/2 x 12 or smaller depending on the design. I tape it over the journaling I just printed using a non-permanent repositionable adhesive. I use Wacky Tac. It is the best I've found. It barely sticks and I only use it for this purpose. Then put your paper back into the printer and print again.
Finally, I put my background cardstock back together and tape together on the back side. You can cover up your seam with ribbon, a row of pics, or a strip of paper.