On the upper right of your screen (above the animation palette) you should see the file palette.  Use this palette to browse through the image folder's you'd created in step one to find the images you'll be using to assemble the initial key-frame. Before you begin using the images you might want to take your time to give each image a custom pivot point. (images default to a top-left pivot point, and its often more convenient and leads to better final results to set pivot-points based on actual aspects of the image in question...for example, the image of an upper arm would scale and rotate more naturally around a pivot point set in the center of the shoulder). To set a default pivot point for an image, double-click on that image in the file palette and a dialogue box will appear giving you the ability to set the pivot point. You can use the quick-set icons at the top right of the dialogue to set instantly and accurately set the default pivot point of the currently selected image to any corner, center, or the middle of any of its sides. Once you've set the pivot point how you'd like, click OK.
Setting Default Pivot Points

Spriter Pro User’s Manual version 1.4

You might end up with several images that use the same size, especially in order for image swapping purposes.  In this case, don’t worry, you won’t have to set the same custom default  pivot point ot them all manually.  Just set the custom default pivot point to one of them, then click the “Copy Default Pivots” button Under the “Currently Equipped Tools” section of the Palette, then multiselect all the images you want to have the same default pivot point and click the “Paste Default Pivots” button.
IMPORTANT: You might notice that once an image is placed on the canvas, you can left-click and drag on the round widget designating the position of the pivot point to change it’s position. It’s very important to know that this sets a NON-DEFAULT pivot-point, which actually tween betweens keyframes. While this feature can be useful, (for example if you need at one point in an animation for an image to rotate around a different pivot point), it can also be very confusion, and might not be well supported by certain Spriter run-times. For this reason we recommend you avoid setting pivot points in the canvas unless you not only need the special attributes of a non-default pivot point and you’re sure the resulting animations will be properly supported by whichever run-time you will be using. (if any)
If you happened to set your images pivot points via the canvas accidentally, and had intended to use default pivot-points, there are two features in Spriter that can help you switch to actual default pivot points.
Example 1) Let’s say you’ve accidentally changed your pivotpoint via dragging the round widget in the canvas, and you would rather that the image use the universal default pivot point which you had previously (or after the fact) set via the proper way mentioned at the top of this section.  Just right-click on the actual round widget representing the position of the pivot point in the canvas and choose “use default pivot point” from the drop down menu which will appear. This will revert the pivot point to the default pivot point, but leave the image exactly where you had placed it.
Example 2) Let’s say you like the new position you’ve set for the pivot point via the canvas and you want to replace the current default pivot point with this new pivot point position. Just right click on the round gizmo representing the position of the current pivot point in the canvas, but this time choose “Overwrite default pivot” from the drop down menu that appears. This will make your new pivot point position the new default pivot point position, replacing whatever the old position was.