Man kan bruge "altså" som et fyldord som f.eks. "well", eller man kan bruge det til at fremhæve noget.
In case other Danish learners are wondering, but won't understand a full explanation in Danish, I'll write in English below.
It can be used as a filler word like "well, ..." e.g. before explaining something to someone or you can use it to add emphasis to something.
A few examples I could think of:
1) "Altså, først er du nødt til at..." ~ "well, first you need to..."
2) "Jeg forstår altså ikke, hvordan det kunne ske" ~ "I just don't understand how it could happen"
3) "Du er altså nødt til at stramme dig an" ~ "you really need to get your act together/make an effort"
4) "Jeg synes altså, at den er rigtig pæn" ~ "I think that it's really pretty" - adds emphasis to your opinion. For instance another person might ask for your opinion before buying because they are not quiiiite sure - or they might not think it's pretty so you state a contrasting opinion.
5) "det synes jeg altså ikke!" ~ "Well, I don't think so!" - you're stating your opinion, others might disagree, but you'll have to agree to disagree, because you won't budge at all.