At the bottom of the screen you will see 3 tabs. Click on the one titled "Upload attachment."
It should look like this:
Now you will need to select which file to upload. In my example it is a screencap I took for this and placed in a subfolder under My Pictures. You will need to be able to find your picture on your computer for this part.
You should now see the file added to the bottom of the thread. Almost done!
Here is an example of adding captions to pictures.
Now click on your post where you want to put your picture. Click on "Place inline" and it will add the BBCode to display your image there. It should look like this (note my file name was 1.jpg but yours will be whatever you named it).
Now your picture will be in your post! Preview helps a lot when you're adding multiple photos or even just to check that you're still doing it right. Here you can see a screencap of the preview to my post after uploading my first image. The rest of my images were added by simply repeating the process.
Feel free to ask if you have any questions about the process, I'll be more than happy to help.
EDIT: I just noticed the sub is specifically for lockpicking tutorials. Sorry if this is the wrong place for this. If you feel like it will help I can put this somewhere else.
"People dont kill people with giant boulders"
"They will if you take away their assault rifles"