Thats good, it's the first step to something fun.
Draw your idea, think of a circuit design.
Don't get stuck on details!
Think of parts you will use
Put it together on paper
It doesn't have to be pretty
But it may be...
Redraw your current circuit in a program of your choice
Look up the dev-boards you've used
The schematic and PCB design of most dev-boards is publicly available
The schematic of an Arduino (source: arduino.cc)
Look at the parts of the dev-board you used
Maybe you didn't use a certian IC so that it can be removed
This will make it cheaper and easier to solder
There's useless logic level converting here...
Look at the parts around your dev-board i.e. shields
Do they have any special components on them?
Lookup the schematics and copy them in to yours
MANY dev-boards have weird compontents on them, which you can't order sometimes...
Look them up online, look at the major parts around them.
Find the datasheets, search (i.e duckduckgo) alternatives
Edit your schmatic accordingly (You may need to add a resistor or two. Or change some connections)
Use your software to place the parts on a bare PCB
Place them in a similar fashion to your schmatic
This will make debuggin much easier
In a later stage you can fit them on a PCB-size you favor
Parts on both sides?: yes and no...
You have parts all over your PCB, but they're not connected
Your software will usually tell which parts have to be connected
Or even do the work for you
If you route by hand:
Don't get frustadted if your first try doesn't work
Make use of both layers
It's like drawing, everyone can do it. You just need some pratice
Your PCB design is ready - Yeah
There are some online shops for ordering PCBs
They usually use GERBER files which you can export from your software
Just order some PCBs in a color and quantity of your choice.
Your PCBs are on the way - You need some parts
There are some online shops for ordering Parts
Lookup and buy your parts at a seller of your choice
Order more parts than you need cause f**kups happen
Your PCBs and parts arrived
You can start soldering now
Take your time
Print out your schematic and design for reference
Start with the smallest and the passive parts
Work your way through all of the parts leaving the most expensive and largest at last
SMD - Surface-mounted device - They are (very) small parts usually used on commercial things.
If you have experience with soldering you can use SMD parts
Choose a size your comfortable with. SMD parts range from a few milimeters to things that you'll never find again
There are useful size charts online or even available as PCBs
That shouldn't be an isssue
You can get cheap but still quite useful soldering kits online
A Hackerspace near you will probably have some nice equipment too
There may even be someone who can help you
Visually inspect your PCB
Make sure ther're no unwanted connections (beep them)
Make sure all parts are solderd properly and have good contact
Try to find the part that didn't work
Was the part broken already
Is something wrong with the connections
Test individual parts of the circuitry
Replace broken parts
Is there an error on the PCB