If you connect Mailchimp and Facebook, you can embed a signup form on your Facebook Page (not just share a link to your form in your timeline), and post to your timeline from Mailchimp.
Connecting Mailchimp and Facebook
Once you’ve logged in to Mailchimp, click on the drop-down arrow next to your account name in the top right-hand corner of the Mailchimp screen and choose Account.

Then, click on the Integrations menu. Scroll down the screen (if necessary) and click on Facebook. Click on Log In, then click on Continue as [Your Name Here].
Click on OK (or Choose what you allow to amend your settings). You should then see a confirmation message –

Adding Your Signup Form to Facebook

Click on the Page to use drop-down menu, then click on the Facebook Page where you want your signup form to appear.

Now, click on the Audience to use drop-down menu, then click on the audience (contact list) that you want Mailchimp to add the details to.

Click Yes to Use signup form tab

Under Form theme, click on the drop-down arrow and choose whether you want to use the design from your Mailchimp-hosted signup form, or a more Facebook-like design.

Type in a label in the Tab label section (the default is “Email Signup”). You can amend this later, if you need to.

Finally, click on Save. You will then see a confirmation message.
Removing Your Signup Form from Facebook
To remove a Mailchimp signup form on your Facebook Page, follow these steps.
Click on the drop-down arrow next to your account name in the top right-hand corner of the Mailchimp screen and choose Account. Then, click on the Integrations menu.

Click on Facebook, then click on the Page to use drop-down menu, and select the Facebook Page you want to remove your signup form from.

Then, click the Audience to use drop-down menu, and choose No audience connected.

Click on Save.
Remove Facebook and Mailchimp Integration

To remove integration between Facebook and Mailchimp, access your Facebook account and click on the drop-down arrow in the top right-hand corner, and choose Settings.

Click on Business Integrations in the menu on the left

In the Active business integrations section, put a tick in the Mailchimp checkbox by clicking on it, then click on Remove.

Click on Remove again in the dialogue box that appears to confirm you want to remove the integration.
This post is available as a downloadable .pdf in the Resources Section of this website. I hope you find it useful!