Go to customisation > report content manager and select the section and then click on the edit pencil of the snippet where you wish to add the image within your report.
You'll be directed to the Snippet Detail page for that snippet. If you haven't already created a custom version of the snippet, click create custom snippet, otherwise click on the edit pencil of your existing custom version of that snippet. You'll find more information about how to create a custom snippet here.
Next you'll be directed to the Snippet Editor. To add an image to the snippet proceed as follows:
1. Position your cursor where you would like the image to appear (see orange arrow in screen shot below)
2. Click the image button (highlighted in red) within the Snippet Editor's control bar.
The Image Properties dialogue box will open like this:
3. Paste the URL where your image is saved in the URL field. (see tip below for uploading and hosting your image on the web).
4. Resize the width and height of the image as required (remember to keep the aspect ratio locked).
5. Click OK and your image will be inserted in the snippet, and added to your report template.
If you don't have a facility to host your images on the web, don't worry there are many free image web hosting services out there. Try typing free image hosting into Google - see what I mean! A particularly easy one to use is postimage.org.
If you do choose to use PostImage - simply select the image file you wish to upload using the Choose Images button in the middle of the screen. Having uploaded the image to PostImage you will then want to take a copy of the https URL link contained in the DIRECT LINK field as you'll need this for step 3 above.