rejoice

Oh yeah I'm aware, I was just pointing him in the right direction

If you're trying to use the API to fetch a non-merchant gateway's payment HTML, see Payments::getBuildProcess as @coreyman mentioned above. The arguments required are the method's parameters.
If you are making a merchant CC payment, look at the other end-points available on the same page.

That's cause it needs 3 values to work not sure which ones though.

I found this -
So I tried accessing an endpoint via the attached image method in postman and it looks like we are on the right track. Looks like the arguments are as follows -
"contact_info" => $contact_info, "amount" => $amount, "currency" => $currency, "invoice_amounts" => $invoice_amounts, "options" => $options, "gateway_id" => $gateway_id This method and docblock can be found in \components\gateway_payments\gateway_payments.php
    /**      * Returns an array of HTML markup used to render capture and pay requests for non-merchant gateways      *      * @param array $contact_info An array of contact info including:      *  - id The contact ID      *  - client_id The ID of the client this contact belongs to      *  - user_id The user ID this contact belongs to (if any)      *  - contact_type The type of contact      *  - contact_type_id The ID of the contact type      *  - first_name The first name on the contact      *  - last_name The last name on the contact      *  - title The title of the contact      *  - company The company name of the contact      *  - address1 The address 1 line of the contact      *  - address2 The address 2 line of the contact      *  - city The city of the contact      *  - state An array of state info including:      *      - code The 2 or 3-character state code      *      - name The local name of the country      *  - country An array of country info including:      *      - alpha2 The 2-character country code      *      - alpha3 The 3-cahracter country code      *      - name The english name of the country      *      - alt_name The local name of the country      *  - zip The zip/postal code of the contact      * @param float $amount The amount to charge this contact      * @param string $currency The current to charge      * @param array $invoice_amounts An array of invoices, each containing:      *  - id The ID of the invoice being processed      *  - amount The amount being processed for this invoice (which is included in $amount)      * @param array $options An array of options including:      *  - description The Description of the charge      *  - return_url The URL to redirect users to after a successful payment      *  - recur An array of recurring info including:      *      - start_date The date/time in UTC that the recurring payment begins      *      - amount The amount to recur      *      - term The term to recur      *      - period The recurring period (day, week, month, year, onetime) used      *        in conjunction with term in order to determine the next recurring payment      * @param int $gateway_id The ID of the nonmerchant gateway to fetch,      *  if null will return all nonmerchant gateways for the currency      * @return array An array of HTML, indexed by the gateway name      */  

This is just a guess, but if you look in \projectfolder\vendors\components\gateways\nonmerchant\paypal_payments_standard\paypal_payments_standard.php you will find 
PaypalPaymentsStandard extends NonmerchantGateway It looks like you are required to have a Blesta invoice to pay to use this gateway, so you will probably need to generate an invoice first.
On line 232 there is buildProcess where I found this information. It looks like it's building the request to paypal. Maybe someone else can shed some more light.