At the right, click Insert.
Select the type of file you want to add, e.g. Docs, Slides, Sheets, Forms, or Charts.
Choose a file > Insert.
To publish your changes, at the top right, click Publish.
At the right, click Insert.
Select the type of file you want to add, e.g. YouTube, Calendar, or Map.
Choose a video, calendar, or place Select or Insert.
To publish your changes, at the top right, click Publish.
You can upload a .jpg, .png, or .gif image file from your computer. To add other file types, use Google Drive.
Upload the files to your Drive first.
At the right, click Insert Images.
Choose a file from your computer Open.
To publish your changes, at the top right, click Publish.
On the right, click Insert Drive.
Choose a file Insert.
To publish your changes, at the top right, click Publish.
Taken From Google Sites Help