YANT (Yet Another Noob Thread)

To offer an alliance you must have 'close' relations with the other race (friendly won't do it). You must also have the Alliances tech researched.
If it an option (you have fulfilled all the requirements) it will show up in the trading window.

And yes, it is possible to combine mods as long as there are not conflicting files between the mods (like duplicate GC2Types.xml or TechTree.xml's). In some cases you can use the folder structure to your advantage. An example would be when you have 2 TechTree.xml files.
You could place one of them in the \Data folder, and also one in the \Data\Techs folder.
The one in the \Data folder completely replaces the game's TechTree.xml, while the one in the \Data\Techs folder adds to the main TechTree.xml that is currently being used.
So as long as you do not have duplicate entries in both files you'll be ok.

I use Kryo's Hull System Mod, to which I have added some techs and ships from the Star Trek mod as well as some of my own stuff (plus some ships from some other mods). So essentially I am combining 3+ mods, which are all combined in the \Mods\KHSM folder structure.

Hi and welcome to the game

To answer your questions: -

1. You need to have researched the 'Alliance' tech and both the other race and yourself need to have the tech. Next you need to raise your friendship level to 'Close', this is done via trading so you need to set up a trade route to the prospective race. A few gifted techs etc can help raise your friendship level too.
One thing to note is your moral standing in the game as most races will only allow an alliance with a race that has the same ethical level or one close to them. I.E.to get an alliance with a good race you need to be good or neutral, being evil would make things really difficult to get an alliance.

2. Yes it is possible to merge more than one mod at a time. I am not sure if the makeup of both of those mods but all you need do is install one of them and then add the other files form the second mod into the folder created by the first mod. It would be advisable to check and make sure that both mods don't use the same file or you will need to change one of the files manually. However most mods work well with each other.

Hope that helps

if i may ask whats the quickest way to have a close relashump with another race
sar spelling long story  

Give them crap. Get some proprietary goodness and share the love - new technologies or new research you've completed. Opening up trade routes with them certainly doesn't hurt, either.

I don't think you can get past "friendly" with gifts.

"Close" comes with having a bunch of +'s in your relationsship with the AI's. When you view your relationships, you will see +'s and -'s, when you have a certain number (7 ??) +'s you will have close relations.

There was a thread that listed all of the things that can be listed and wheter it was possible to get one or 2 +'s. Sorry but i don't know where it is exactly.
Some of these are:
you need to trade with them
have a much stronger military
great diplomacy
share treaties
a long relationship without comflict
share the same ethical alignment
gifts can help you get to fiendly

there are more, and then there are some that give you minuses, like close borders etc.

You don't necessarily have to have pluses in EVERY category just enough of them. Of course the more you have the better. An example is the same alignment. You CAN have an alliance with races of differing alignments, but you will need to compensate with more pluses somewhere else. Hopefully you can get enough to overcome the minuses.