Before you add an image, make sure that it is the correct size and shape for your web page, and that the file size is optimized for the web. If you put an image with a very large file size into a wiki page, it will take a long time for users to download it. Many image editing programs will allow you to compress images for the web.
Go to Wiki.
Select the Wiki tool from the Tool Menu of your site.
Click Edit.
Select the Image icon in the editor toolbar.
Select the image from Resources.
Click the Select link for the image file if it is already in Resources.
Or, upload the file.
If the image file is not already in Resources, click Add > Upload Files in the Add drop-down menu to drag and drop or browse for and select the file you want.
Click Continue.
Once you have selected the image file, click the Continue button.
Preview content. (Optional)
If you would like to preview your content before saving, click the Preview tab at the top of the editing area.
Click Save.
Once you have finishing editing the page, click Save.