Hey guys,
first you should read up on
how to setup a multilingual site with Joomla.
Next step is the multilingual setup in SEBLOD. trip already pointed out how to do that. Here in a more detail:
Go to SEBLOD Options.
There in Language tab set "JText" to yes.
Now when you create a new field, for example my_field and leave the label empty, SEBLOD will name the label something like COM_CCK_MY_FIELD.
Now in your Joomla installation's language/overrides folder you create an override file for your language. For German that would be de-DE.override.ini. Inside that file you create a line:
COM_CCK_MY_FIELD="My field Lable";
Do the same for your other language(s).
You could also use the Joomla Adminsitration: Extensions->Language Manager->Overrides and create your overrides there.
Now SEBLOD will take the translations for the labels depending on the language in the Frontend.
To make your Input forms save your fields for different languages, you would need to include the field "Article Language" in your content type form. As an example take a look at the standard "Article" content type.
When adding/editing content you can now choose a language and your inputs will get saved for that language.
There is some further reading
here and
here and
here. A Google search for "seblod multilanguage form" could have taken you there.
The rest you will have to figure out yourself, I guess. Documentation and support for SEBLOD is still far from good. If you have further questions you can always try to post them here. If your lucky you will even get an answer. (Not that I'm being sarcastic or frustrated about the support situation myself ;-) )