OK, 150mm mirror, f5 750mm fl - good news - no inbuilt barlow lens. Should be easy to collimate when you need to.
Your star was maybe Vega, perhaps Altair. But not a good idea to look with something low to the horizon to focus and adjust - think of all that horrible moving air you are looking through, disrupting the light coming to your scope! Go with something higher in the sky.
Look at at about 40 deg above the horizon, to the east about 8pm. Look at the brightest object in the sky there, not too far from the Moon. Jupiter!
To look at some stars, turn to a bit west of south and look at the Southern Cross stars - up at about 50 deg above the horizon, they will be better to practice your focus on. Try the uppermost of the two pointer stars when you have the scope well focussed on other stars - with the 6.5mm eyepiece when you get the star centred.
