Even saying , to sell high buy low sounds weird to me. In most instances, selling means
1) cutting loss
2) taking profits - partial or full
Now, selling means an entry position, hoping to buy back later at lower price. That takes practice , at least for me. Honestly, many many practices as it is a different ball game altogether.
If you have never short stocks, , currencies, cryptocurrencies thus far, I suggest you open a demo account and start to practise. In due time, it would come handy.
The usual applies, Stop loss, risk management, position sizing, strategy, etc