Mi uzas la kompason por orientiĝi.

Because la kompason is the direct object of uzas.

• Mi uzas ... = I use ...
• The thing being used is the direct object.
• In Esperanto, direct objects take -n.

So:

• kompaso = compass
• la kompaso = the compass
• la kompason = the compass (as a direct object)

Yes, you could say kompason, depending on the context.

• la kompason = the compass, a specific compass
• kompason = a compass or compass in a more general sense

So:

• Mi uzas la kompason por orientiĝi. = I use the compass to get my bearings.
• Mi uzas kompason por orientiĝi. = I use a compass / I use compass to get my bearings.

Esperanto uses la only for definite meaning, like English the.

uzas is the present tense form of uzi.

• uzi = to use
• uzas = use / am using

The ending -as always marks the present tense in Esperanto.

So Mi uzas means:

• I use
• I am using

Esperanto does not normally make a separate distinction between simple present and present progressive the way English does.

por means for or in order to.

Here it introduces the purpose of using the compass:

• Mi uzas la kompason por orientiĝi.
• Literally: I use the compass for becoming oriented.
• Natural English: I use the compass to orient myself / to get my bearings.

A very common Esperanto pattern is:

• por + infinitive

For example:

• Mi venis por helpi. = I came to help.
• Ŝi studas por lerni. = She studies to learn.

Because orientiĝi means to become oriented / to get oriented / to find one’s bearings, while orienti usually means to orient something or someone.

So there is an important difference:

• orienti = to orient, to point, to align something
• orientiĝi = to become oriented, to orient oneself

In this sentence, the speaker is not orienting some other object. The speaker is trying to become oriented themselves, so orientiĝi is the natural choice.

-iĝ- is a very useful Esperanto suffix. It often means:

• become
• get
• come to be
• a change into a state

So:

• orienti = orient something
• orientiĝi = become oriented

Some similar examples:

• varma = warm

• varmiĝi = to get warm

• ruĝa = red

• ruĝiĝi = to become red / blush

• sidi = to sit
• sidiĝi is not standard, but with many verbs and adjectives, -iĝ- gives this “become” idea

In your sentence, orientiĝi has the sense of getting one’s bearings.

Because orientiĝi already carries that idea.

In English, we often say:

• orient myself
• get myself oriented

But Esperanto often uses -iĝ- instead of a separate reflexive object.

So:

• Mi orientas min. = I orient myself. (possible, but less natural here)
• Mi orientiĝas. = I get oriented / I orient myself. (more natural)

That is why por orientiĝi works without adding min.

You probably could be understood, but por orientiĝi is more idiomatic in this context.

Why?

• orienti min sounds more like to orient me as an object
• orientiĝi naturally means to become oriented oneself

So for finding your bearings, orientiĝi is the better choice.

A good rule of thumb:

• if the subject is causing a change in themselves and Esperanto has a natural -iĝ- form, that form is often preferred

No, Esperanto word order is fairly flexible, although this sentence uses the most neutral order:

• Mi = subject
• uzas = verb
• la kompason = object
• por orientiĝi = purpose phrase

This is the standard, clear order.

You could rearrange parts for emphasis, for example:

• Por orientiĝi, mi uzas la kompason.

That still means the same thing, but it emphasizes the purpose first.

It is a normal Esperanto word. Many Esperanto words come from international roots, and kompaso is one of them.

That is very common in Esperanto:

• telefono
• radio
• motoro
• kompaso

So even if it looks familiar to an English speaker, it is still a regular Esperanto noun:

• singular noun ending: -o
• plural: kompasoj
• accusative singular: kompason
• accusative plural: kompasojn

A rough pronunciation is:

Mee OO-zahs lah kom-PAH-son por o-ree-en-TEE-jee

A few helpful points:

• Mi sounds like mee
• uzas has stress on U: OO-zahs
• kompason has stress on PA
• orientiĝi has stress on TI

Remember that Esperanto stress is almost always on the second-to-last syllable.

Also, ĝ is pronounced like the j in judge or jam.

So in orientiĝi, the final part ĝi sounds roughly like jee.