Eat from around the outside of the cup first. The heat from your hands will melt it, and it will be easier to eat.
この場合、次のような言い方ができますよ。
ーEat from around the outside of the cup first. The heat from your hands will melt it, and it will be easier to eat.
「カップの外側から食べな。手の熱で解けて食べやすいよ」
the heat from one's hands で「手の熱」
ご参考まで!