You need to edit "bg.png" in a graphics editor like Photoshop or Irfanview. I simply edited the height (leave the width at default) to 1080 (since my desktop is 1920x1080) and saved the file replacing the original, then refreshed the skin to see the changes. Hope that helps!
1.Copy the S7DE folder from the zip file to your Skins folder, 2. Go into the Manage screen for Rainmeter and find the "Create .rmskin package" button near the bottom-left. 3. Give the package a name, 4. add an author's name, 5. click the Add skin... button, 6. Select SIDE7 from the dropdown and click Add. 7. Select the "Load Skin" option in the "After Installation" section 8. Choose your version of Windows 9. and click the Create Package button.