Usernames are currently only visible in the old Explorer. To view usernames in the old Explorer you own you may search for your username in the top search bar. Then click on the Subdomain Registration. Copy the “Address” field (a long string like 1FnNvQ36tGsi8UHp2E5CmCs3uF8RvjLWJ2 ) and then paste it into the search bar. The results will show any IDs registered with that address.
You may also search for your Blockstack ID using this link, swapping your ID in for “your_ID” https://core.blockstack.org/v1/names/your_ID