Disclaimer: I work for AgileBits, makers of 1Password
If you have any specific questions about 1Password let me know. Happy to help however I can.
On our iOS app you can create new items directly from the application, or if you're on a webpage in Safari you can invoke the Share sheet and then open 1Password's extension which will allow you to create a new login, and on most pages it will also grab the username and password from the page and pre-fill them into the login item. The sites it won't work on are those that insert their login forms inside of iframes.