Go to your Google advertising account. Click the Tools and Settings icon. Then click + to create your conversion. Select and create a website conversion. Then select the option to add with Google Tag Manager. Copy the conversion ID and conversion tag.
Then point to forms.app and select the form where you want to track the conversions. Click to the form's settings, open the Google Ads Conversions tab, and copy your conversion ID and conversion tag into this field. That is all. Now you can optimize your campaigns according to form submissions with your Google Ads account.