Go to Wiki.
Select the Wiki tool from the Tool Menu of your site.
Select the Image/Attachment icon in the editor toolbar.
Select the file from Resources.
Click the Select link for the file you want to attach if it is already in Resources.
Or, upload the file.
If the file is not already in Resources, click Upload Files in the Add drop-down menu to browse for and select the file you want.
Once you have selected the image file, click the Continue button.
(Optional) Repeat as needed to attach additional files.
Preview content. (Optional)
If you would like to preview your content before saving, click the Preview tab at the top of the editing area.
Once you have finishing editing the page, click Save.