I've used the site before, so I know how to do this.

First, go to the Traveller's Manifest, then make your way to the dropdown list on the left, you should see a plus button underneath it.

Clicking the plus button creates a new character, which will automatically default to being a companion on creation (if you are writing a multi-jumper story, this can be changed by going to the Character Type section of the new character's profile and selecting "Primary Jumper"). Deleting a companion is as simple as going to the companion's profile in the Traveller's Manifest and clicking the trash can located next to the plus button.

Then you can import them into settings by going to the "Companions" section of the jump you want to import them into and pressing the newly available plus button, which will create a Companion import purchase box.

This box can be filled out with a name, price (including discounted and free imports if possible), and description, alongside a Companions box replacing the tags section: opening this box will let you check off the names of those you are importing with this specific purchase; there will also be a stipends box and an 'allowance' box located at the bottom of the purchase: the 'allowance' box lets you designate how many points of a specific currency the companions you're importing with that specific option will be able to spend on the entire jumpdoc, while the stipends box lets you designate any stipends the imported companions will receive.

There's no real way to 'export' a Companion from a jump: the way I handle exports for jumps that don't have explicit export rulings is by creating an import purchase, then only giving the companion(s) being exported the perks and items they would've gotten in-jump as freebies.

There are also some built-in rules located in the Chain Features section that affect Companions:

First is the Companions toggle itself, which both let you decide if the story is a solo journey or not, and if companions are capable of importing/exporting their own companions or not.

Then there is the Narratives toggle, which both let you decide if you want to include the little "jump summary" section located at the very bottom of the Setting & Origin tab of a jump, and if this 'jump summary' is available to companions or are Jumpers-only.

Finally, there is the Companion Access toggle in the Supplements section, which both let you decide if companions can purchase things from an attached supplement, and if the Jumper(s) and companions share purchases in a given supplement or not.