Nice picture. From the EXIF data of the picture I can tell you, that it should be an autofcus lens.
It should be this one:
Sigma 18-50mm F3.5-5.6 DC Lens Reviews - Sigma Lenses - Pentax Lens Review Database
Bad news is, it is not regarded very highly. Good news is, it is better then the Tristar probably.
Still better, it is better then no lens and good for a start, so do not worry. First thing will be to learn how to use the K-10D which is not a bad camera.
You have been using M - manual mode. You should use it in auto mode first. Set the camera as follows and get out and do do some pictures.
If you feel confident explore the camera further. You can always come and ask for more information,
Reading the manual will give you faster results eventually.
Set the wheel on the left on the top of the camera to the green symbol. The camera will then do a lot of things for you. Mainly select the aperture and time for a correct exposure,
Set the switch under the wheel to the green symbol, which is matrix metering. Should work better then weighted metering (the next to the left).
Set the switch on the left side of the bayonet to AF.S - This is single shot auto focus. Be prepared, that you can only take a picture if the camera can get the lens into focus,.
Set the wheel around the "OK" button on the back to the most left green symbol. The camera will try to figure out which AF point to use. This will probably go wrong quite often. I fto an anoying degree, switch to the symbol on the right, where you can only use the center AF point.
Set the switch on the back under wheel with the "OK" button to "ON". This will turn on the shake reduction.
Basic settings for beginners done. Now choose your subject. Press the shutter slightly down. The lens should go into focus, which is indicated by a red flash in the viewer, which will showe you the focus point and maybe a beep. Press shutter fully down. Picture should be okay.
I would love to tell yo a bit more on white balance and ISO settings, but the batteries of my K-10D are empty. And when I rember it right you can not change ISO in the green mode. You have to switch to "P" program mode, which is essentialy the same, with some freedom.
Take pictures! Have fun!
And welcome to the forum!