Navigate your browser to the following free image hosting website: imgur.com.

Step 1:
Click on the Computer button:





Step 2:
Browse your computer and choose the image you want to upload:





Step 3:
Click "Start Upload".





Step 4:
Wait for Uploading Images to complete:





Step 5:
Upload Complete, Copy Linked BBCode (message boards):
- Right click the code and choose Copy.





Step 6:
Now that you have copied the link, you can paste it directly into your thread.

Example: