Hi.
For the spelling, right clicking a word that is reported as misspelled there is a “learn spelling” menu item that adds the word to the dictionary.
You may also “ignore spelling” if it is only for this one project.
As for auto-complete suggestions, that is in the project settings. Auto-complete list.
Either manually add all your desired completions to this list, or right-click in the editor, again, there is an menu item to add them one at a time as you think of them.
[EDIT]
…And I almost forgot : for auto-completion to work you need to have it activated in the options.
Options / Corrections / Corrections → Suggest completion as you type