Venture (like other free Shopify -themes) shows the payment icons determined by your payment settings automatically. So when you have enabled some payment methods, they should be automatically visible in the footer. If they are not, check that the setting is enabled by navigating to the Theme -> Customize -> Footer and checking the box that says "Show payment icons".
You can also edit Liquid to show the desired icons without enabling the actual payment settings. Instructions can be found here, if you are comfortable editing code: https://help.shopify.com/en/themes/customization/store/add-credit-card-icons
Freddie here from the Shopify Support team, happy to help out.
If you've tried following the instructions outlined in those documents and it's still not working for you, we can have a look for you if you are using the Venture theme as it's supported by Shopify! You'll just need to send in an email to firstname.lastname@example.org so we can check out your store and possibly escalate this issue up to our Theme Support team for further help. Once you send in that email, feel free to comment back here what your ticket number is so I can locate your email to look into this for you!
Shopify Support - email@example.com
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