You want to have this "pin it" button on your Weebly site. These are the easy steps that you can follow.
Step 1
You can get Pin it code in here. Then follow the instruction through this picture.
Step 2
Go to the Pages setting then choose in which pages you are going to put the pin it button. Click the advanced setting. Copy paste the code on the "Footer code" area. Then Save it. That's it.