1. Taking the Screenshot

On most operating systems you can take a screenshot by pressing the Prt Scr key on your keyboard. If you’re on a Mac, just Google it. Somehow you need to either get the data copied to your clipboard or saved to a file that the GIMP can edit. On Windows Prt Scr will seem to do nothing, but it actually copies the data to your clipboard.

2. Open it Up

Now open the GIMP. If you saved the screenshot to the file open it up as a file. Via File -> Open. If it was saved to your clipboard then open it via File -> Create -> From Clipboard Now that we have our screenshot opened we can edit it. But before we do that, why not save it in GIMP’s native file format so we can preserve our layers and other data. Do this via File -> Save As and then call the file whatever you want. Just make sure you put the .xcf extension on the end. Here is mine.

3. Crop

Select the Crop tool. Now you can select the area that you want to crop. Here’s a tip: Make the focus of your screenshot be in the middle. You might also wanna leave some extra room around the edges, so don’t crop it too tightly! This is what I have after cropping.

Go to Step 4 if you want to do the dim and blur edit or if you prefer using text and arrows in your screenshot go down to Stop 5.

4. Dim and Blur

Maybe you just want a simple screenshot and you only want the user to see (or at least focus) on a certain part. Here’s how we can do that.

First you’ll want to make a selection around the part where you don’t want it to be blurred. For me, it will be the Google logo. You can select with the Rectangle Select Tool. Cut that selection to your clipboard via Ctrl + X. Paste you image back into place using Ctrl + V. You’ll see now it is on a floating selection. In the Layers window, select the floating layer and then click the new layer button. This will create a new layer with our selection on it. You can now deselect using Shift + Ctrl + A. Now create another layer. This one should be between your other two. Use the Bucket Fill Tool to to fill our layer with black. (Make sure black is set as your foreground color.) Change the opacity of that layer to whatever you want. But I’m going to set mine to 60 percent. This is what I have so far.

Now let’s blur. Select your bottom-most layer. And then go to Filters -> Blur -> Gaussian Blur. I used the following settings.

And there you have it! Here is my final result. You might wanna change things around to your liking.

5. Arrows, Drop Shadow, Text, and Rounded Rectangles

I see you’re taking the more complex approach. I commend your enthusiasm. Let’s get started. Create a new layer over top of the old layer. Go ahead and create a selection that you think will be big enough to hold your text with the Rectangle Select Tool. Once you’ve done that fill it with white. Then use the Rounded Rectangle (Select -> Rounded Rectangle) tool to make the edges rounded. I used the following settings.

Now let’s add a drop shadow to make this stand out from the rest of the image regardless of the background. Use Filters -> Light and Shadow -> Drop Shadow to add your own drop shadow. I recommend the following settings, but you can make it however you like.

After that, I have something like this:

Make sure your layer with the white is selected in the layers window and invert your selection with Ctrl + I. Then hit the delete key on your keyboard. You can also deselect your current selection via Shift + Ctrl + A. Now let’s add some text. Use the Text Tool to put some text over top of your little “bump”. I have something like this. Here is what I did.

Looks pretty good so far, but let’s add an arrow. You can create one with the Pencil or Paintbrush tool. For best results make a new layer for this and place it between the white block layer and the drop shadow layer. The drop shadow should be under your new layer and the block layer should be over it. This requires a pretty steady hand, but don’t worry about it. It adds a “homemade feel” to it. If you really want a real arrow though, Google is your friend. This is what I came up with:

Conclusion

Hopefully, you can draw your own conclusions but let’s recap on what we did.

1. We took a screenshot.
2. Imported it into the GIMP.
3. Added Drop Shadows and all kinds of other good stuff.
4. Survived.

Not much really (if you exclude the fourth), but hopefully it also taught you some of the basic tools of the GIMP. Keep designing.