<div class="float-contact"><button class="chat-zalo"><a href="http://zalo.me/0382032166">Chat Zalo</a></button><button class="chat-face"><a href="http://m.me/trongraunuoicatainhahcm">Chat Facebook</a></button><button class="hotline"><a href="tel:0382032166">Hotline: 0382 032 166</a></button></div><style>.float-contact{position: fixed;bottom: 20px;left: 20px;z-index: 99999;}.chat-zalo{background-image: linear-gradient(to left, #40E0D0, #1E90FF);border-radius: 20px;padding: 0 18px;color: white;display: block;margin-bottom: 6px;}.chat-face{background-image: linear-gradient(to left, #4169E1, #0000FF);border-radius: 20px;padding: 0 18px;color: white;display: block;margin-bottom: 6px;}.float-contact .hotline{background-image: linear-gradient(to left, #d11a59, #A52A2A);border-radius: 20px;padding: 0 18px;color: white;display: block;margin-bottom: 6px;}.chat-zalo a, .chat-face a, .hotline a{font-size: 15px;color: white;font-weight: 400;text-transform: none;line-height: 0;}@media (max-width: 549px){.float-contact{}}</style>


Flatsome:
Advanced - Global setting - Footer

 hoặc có thể chèn vào footer bằng plugin Insert Footer and Header.

 Nhớ minify trước khi up.