Starting out...

When you have TortoiseSVN installed and rebooted your computer (I dont think you have to do that though)
go create a folder somehere you want, like C:\SVN\ .

Now right click that folder and you'll see this in the popup menu:

+-----------------+
| SVN Checkout... |
| TortoiseSVN  > |
+-----------------+

Press "SVN Checkout" and this will window will appear, fill it as below:

+--Repository---------------------------------------------------+
|                              17101986                                            |
| URL of repository:                                            |
| +-------------------------------------+                      |
| |https://OpenSVN.csie.org/yourproject | [...]                |
| +-------------------------------------+                      |
|                                                              |
| Checkout directory                                            |
| +-------------------------------------+                      |
| |C:\SVN                              | [...]                |
| +-------------------------------------+                      |
| [] Only check out the top of folder                          |
| [] Omit externals                                            |
|                                                              |
+--Revision-----------------------------------------------------+
|                                                              |
| (x) Head revision                                            |
|                    +-----------------+                      |
| ( ) Revision        |                | [ Show log ]          |
|                    +-----------------+                      |
+---------------------------------------------------------------+
|                                  [ Okey ] [ Cancel ] [ Help ] |
+---------------------------------------------------------------+

Press "Okey" and then press "Yes" in the messagebox that will appear.
Wait for it to dowload all files for you... And then press "Okey".

Now you have all the files within this repository 😊

Go make a folder named SVN Backup (C:\SVN Backup).
Copy all files in your SVN dir to this dir. Its always good to have a backup.

Now we go on with using SVN.
If you look at your SVN folder you can see that it has a green thing on the icon,
if you modify any files within this folder you will get a red exclamation mark instead,
this is good if you cant recall if you changed anything or not.

If you edit/fix anything I guess you want to upload it to the SVN, then do like this:
Right click your C:\SVN folder and now you will see:

+-----------------+
| SVN Update      |
| SVN Commit      |
| TortoiseSVN  > |
+-----------------+

Press "SVN Commit" and a new window will appear.
In this window you can select wich files you want to upload/commit.
You will see all files you have modified or added, select them and press "Ok"
Wait for it to upload your new files, then press "OK". DONE

Hope this helps out!

There is other thing you can use too, but I think you can figure that out!