These instructions are for a Windows computer but it should be much the same on, say, a mobile phone:
Go to
https://imgbb.com/
Click on the blue 'Start uploading' button.
Click the green 'Upload' button.
Place your cursor in the box at the foot of your screen, which contains a link. A 'Copy' button will appear in the top righthand corner of the box. Click on it.
Come back to answer this post. Right-click in your post and select 'Paste' to put the link into your post.