Hi,
First of all, you have to change the size of the image you want to use, edit it in an image editing program so that it is exactly the dimensions you want to use in your signature.
- In the Outlook click the Signature button in the Include group on the Message tab.
- Press to the Signatures item in the drop-down list.
- In the Signature & Stationery dialog box, select a signature and add a logo or picture in the choose signature to edit box.
- In the Edit Signature section, position the tab where you want to insert a logo or picture.
- Click the Image button. In the Insert Picture dialog box, select the logo or picture you want to insert and click the Insert button.
- After you hit the Insert button, you will see the logo or image inserted into the signature.
- In the Signature and Stationery dialog box, hit on the OK button.
With the help of these steps you can easily get your solution. So, i hope it will good to resolve your issue.