For this you're going to want to start off with four things: Glue, 2 paint brushes(you can use a normal one, but the sponge kind tend to work better), a notebook (again, you can use whatever kind you want, but the composition ones usually look better), mod podge aka the greatest thing ever made. and a variety of magazines, stickers, scrap booking paper, etc.

First, you're going to decide if you want to put paper as a background for your new notebook, or if you're just going to go with the collage method. After that you want to cut out anything within the magazines that you really like. Then you're going to place them on your notebook and move them around until you find a design that you really like. Next, you're going to place glue on the back of your cutouts using one of the paintbrushes and place them on your notebook. Make sure you smooth them out nicely, but not with too much force because they will rip. Then as soon as you're done gluing them on you want to take your other paintbrush and go over the cutouts with the mod podge. Try not to use an excessive amount, but don't worry when it's white at first, it will dry clear. Then you just allow your notebook to dry and repeat with the mod podge if you feel like you need to.