Not sure what goes wrong there, make sure you click "TES Construction Set.exe", to have a plugin activated ingame you must start the game, then in the menu where you can choose Play, Data Files, Options etc. select Datafiles, then doubleclick on the plugins you wish to use.
How to create a race depends on the other programs you have.
If you're just going to use the CS here's how it's done.
First go to 'file', then 'data files' then doubleclick all Masterfiles/plugins you want (many mods offer extra races that you may want to use), then click 'Ok', remember that when you save this as a new plugin it will require the other used files.
Now go to 'character', then click 'race'.
Selecting any of the existing races allows you to change them, to create a new race click 'new' and type the ID-name (this name is for modding purposes only and will not be seen ingame), now you can give your race a name.
You can also give skillbonusses, choose from the available skills and then type how many bonuspoints this race will start with.
Furthermore you can adjust the height, weight and base atributes for both male and female, increasing weight also increases damage taken from falling
.
To add spells you must select 'spellmaking' in the Object Window, here you have a list of all the available spells, just drag the spells you want into the race window under 'Specials', to remove spells from this window select and press delete.
Aside from the normal casting spells there are several other types of spells: 'Abilities' (These will permanently "enchant" you), 'disease' and 'blight disease' (These will also permanently affect you, blight disease is considered more severe ingame, because these diseases are racial features they cannot be cured), 'curse' (Another permanent type of spell, a non-racial curse can be cured, but not by conventional curespells
), 'power' ( a spell you can cast once a day, this spell will always succeed, unless for example a fire-immune beast is targeted by a fire-damage power
).
You may also want to type a description for roleplaying purposes, this text can be read ingame but will not affect the game in any other way.
There are also two checkboxes, 'playable' and 'beast race'.
Playable allows the player to select this race to play with, if not checked then only NPC's can be of this race.
Beast race disables the race's ability to equip footwear and headwear (unless you script this otherwise, but I haven't figured out how
).
Finally click 'Ok' and you have the base of your race, now you must give it a body.
In the 'object window' select 'bodypart', notice that there are different types of bodyparts like armor (which really is armor and not a bodypart).
Now unless you have a program to make your own, you're going to use existing bodyparts.
Scroll untill you see a race that you want to use bodyparts from (you may also select armor or clothing so you can create for example a race made out of glas armor pieces
).
Rightclick on the ID and choose to 'edit', change the ID (if for example you chose a breton head and don't change the ID for the new race than this head will not be shown for the bretons, resulting in some headless people in your game
).
Also select the race that will have this bodypart, if the bodypart was originally armor/clothing change it's parttype to 'skin'.
Exept for heads and hair there are no bodyparts that come in multiple kinds for a race, this is because when you start a new game you can only choose gender, race and head/hair.
You may have already noticed you can choose this bodypart to be either 'normal' or vampire, when this race is aflicted with vampirism and transforms their appearance will change from 'normal' to vampire.
Furthermore there are three checkboxes, two of which you can guess their function, 'blocked' means that you can't edit this unless you uncheck this box and click 'ok'.
Lastly you can decide where this particular bodypart is going to be, it's not advisable to change this, if for example you put an Argonian tail on the place of the foot it's going to look seriously weird ingame.
I mentioned before that you can use armor/clothing bodyparts to make a body, this can also been done the otherway as you can design fashionable helmets made from Dunmer heads (nice disguise, but you won't fool anyone ingame since it is considered a helmet and not a head).