"Mädchen, steigt ein!"
@Christian has it all right!
And yes, the German language has several compound verbs and we are working on better dictionary hints for them. Until that's solved, you should only rarely see compound verbs in our sentences. However, you can always check if a preposition is following a conjugated verb and try it out as a prefix to that verb to identify possible compound verbs.
For example, "Sie steigt ein." where "ein" (in) is the preposition that is part of the compound verb "einsteigen" (to get in). Or for example "Er geht aus." where "aus" (out) is the preposition that is part of the compound verb "ausgehen" (go out). Or lastly, "Meine Eltern geben im Urlaub Geld aus." where aus" (out) is the preposition that is part of the compound verb/expression "Geld ausgeben" (to spend money) - and the prepositions comes all the way at the end.
It's getting easier to recognize the compound verbs. Just have to keep an eye out for the prepositions at the end of the sentences.
Yeah but that's still boarding, I meant in a context where you aren't boarding some form of transportation
sigh I have no idea why "steigt ein" means get in. As I peeked the translation from the word "steigt", it means to increase. There must be a reason for this.
"einsteigen" is a separable verb. Duolingo's dictionary doesn't recognise these verbs as one unit. You'll need to use a proper dictionary. I recommend http://www.pons.eu/
Some resources on separable verbs:
I guess they updated it. Now it recognizes "separable verbs" (is that the term really).