@katsomeday
You can set up embed form in Klaviyo and then add that to a page on your website. Then you can promote that page and wherever you like. That form will be linked and subscribing people to Klaviyo list.
Then create a flow in Klaviyo triggered by that list and in the flow add an email where you provide the link to the resource you promised.
So the process for them would be.. they subscribe to the form on your website and automatically receive the email with the resource guide through the flow and also now you have their email in klaviyo.
Btw just a warning, free product subscriptions together with giveaway subscriptions are the worst subscribers. They usually come for the free stuff and are not much interested in your store so after they get what they want they immediately unsubscribe. This can hurt your account deliverability.
So my suggestion is just set an pop up opt in forms on your website like home page pop up or exit intent pop up for your products page so only people really interested in your brand can see them and subscribe.. In email marketing more subscribers is not always better. They need to be interested in what you are selling for email marketing to be useful.