You do need SSL on your website if you want to embed your donation form onto your webpage or use the popup modal donation form. If you are just linking your secure donation page (using the following link format: https://donorbox.org/your-campaign), you do not need SSL.
Weebly provides free SSL. To install it, follow the steps here: https://hc.weebly.com/hc/en-us/articles/115010923107-Enable-SSL-for-Your-Site.
If you don't want to install SSL, you can simply link your donate button to your https://donorbox.org/your-campaign secure donation page. Click here for step-by-step instructions on how to do this. You can also embed our donation button using Weebly's embed code function.