In the Harmony ONE browser extension wallet:
1. Click TOKENS
2. Click + at the bottom
3. Copy/paste the contract address
4. Click add token
Here are the contract addresses for uONE tokens and HRC20 »»»
UP 👉 one1u0zxuhm69tfl0e5ujtltrj99mpr04xm0judmux
uUP 👉one1qhf662hg6yk70amychdf6s8eu44ywaemkxvc36
BUSD 👉 one1u9mwheravgdesjnnqd4emfwcx3q3aae5hw36l2
uBUSD 👉 one19l0qpe629p5j2kt7vpnh204z374x7k2ljyj0ka
SEED 👉 one10y76c0kyj6d9hmngf0859yx49l4c75d5z77zxr
uSEED 👉 one1eaqywaj45ayxlzwap27rw9fqfryy7377a9ua4z