Step 1 — Create your signature
Create your email signature in Mirosign.com.
Step 2 — Open the Yahoo.com signature settings
Login to Yahoo.com in an another browser tab
Click Settings cog ⚙️ on the upper right-hand side
Select More settings
Select Writing Email from the left side menu
Switch on the Signature for your yahoo email address
Step 3 — Copy your signature
In another browser window return to Mirosign.com and click Download HTML.
Open the downloaded HTML file in a Google Chrome or Firefox, Microsoft Edge (Not Safari as it may cause formatting issues)
Click anywhere on the signature and press Command+A on Mac or Ctrl+A on windows, to highlight the entire signature.
Then copy the entire signature by
right clicking on your mouse Copy or,
Ctrl+C on windows or
Command+C on Mac
Step 4 — Paste your signature
Return to yahoo.com on the other page, click in the signature box and
right click on mouse to Paste or
Ctrl+V on windows or
Command+V on Mac
You should end up with something like this above
Click back to inbox and then Compose to test