Learn Hardcore Finnish: Pystytämme teltan ennen pimeää.

It is from pystyttää, which means to set up, erect, pitch. In this sentence, Pystytämme means we set up / we are setting up / we will set up.

The ending -mme shows we. The dictionary form has tt (pystyttää), but in this conjugated form you see only one t: pystytämme.

Why is the verb in the present tense if the meaning is future?

Finnish usually does not have a separate future tense. The present tense is very often used for future meaning when the context makes it clear.

Here, ennen pimeää (before dark) gives a future time reference, so English naturally translates it as We will pitch the tent before dark.

Is pystyttää the same as pystyä?

No. They are different verbs.

pystyä = to be able to, can
pystyttää = to set up, erect

They look similar, so learners often mix them up.

For example:

Pystymme pystyttämään teltan. = We can set up the tent.
Pystytämme teltan. = We set up / will set up the tent.