The short answer for Countries not in North America / South America / Oceania is that it doesn't work.
Here is the link to Migration entry in the Wiki
http://www.victoria2wiki.com/Migration
Basically each pop in a state will roll to see if they want/need to move. So there are base factors:
Internal (Your State -> Your State) = 1.00%
Colonial (Your State -> Your Colony) = 0.25%
Emigration (Your State -> Another Country) = 0.50%
Your first trick is to get your people moving period. The main factors in this are:
High CON = If your people know their lives suck they will move. If they are ignorant dirt farming peasants they don't know a better life is possible so they won't move.
Needs = If your people are getting all they goods they want where they are they won't move. There are two reasons why a POP doesn't get a need filled:
01. The Good(s) aren't available for purchase
02. The Good(s) are available but the POP can't afford the good. - Usually this is the the case when your population is flowing this stems from where they work either in a factory, as an Artisan, or in an RGO. They don't earn enough from their "job" so they can't buy the goods they want so they look for a new job.
Unemployment = no jobs in the Province so the POP has to move to find work.
There are big negative modifiers for Colonial States so that the natives and any POPs that did move to a colony, stay put.
After the roll to determine which type of Migration / Immigration is done and if they POP decided to move then a roll(s) are done to determine where the pop goes.
Worst Case:
The POP decided to leave your country. They are gone. They roll to see which country they move to. Which is VERY likely to be a Democracy in the Americas with Universal Suffrage and already has a few of the same POPs culture.
Neutral:
Your POP decided not to migrate
Okay:
Your POP decided to migrate to another state in your Country. The POP will roll to determine which Province to move to. They like places with high population, state capitals, coasts, nice terrain, nice life rating, has jobs (factories preferred), and people in the province like them (Culture and Religion).
Best Case:
Your POP decided to migrate to one of your colonies. YAY! The same sort of factors go into choice of province but many of them aren't actually met. Fortunately once a POP has decided to go to a colony they WILL go to a colony.
If your Germany is doing well then most of your people aren't going anywhere you need to use the shotgun approach to get people to migrate to your colonies. Basically you are going to loose WAY more population to the New World but a few will go colonies. You should be increasing population growth through techs this will hopefully make up for those who leave and more.
If you have control over factories find a State with high population (working in factories) and fill up your 8 types of factories. Then close and keep closing down those factories (Capitalists might try and reopen them). This is going to put a lot of people out of work. YAY! These unemployed masses will start to move. You are going to loose huge chunks of them to the new world but again a few of them will choose to move to your colonies.
As you get a few POPs of your accepted culture(s) into your colonies any POP that doesn't have a culture core in the Province might Assimilate. For Algeria this means that Algeria's accepted POPs won't assimilate. Most of the un-colonized land at the beginning of the game don't have any cores, a few do like some provinces near Ethiopia. So if you get enough people moving you might eventually turn a few African Colonies into states. Here is the assimilation link:
http://www.victoria2wiki.com/Assimilation
As Germany you probably should have just left Algeria to the Dirty French. It is all but impossible to turn it into a state as anyone but the French.
Finally to actually answer your question when your POP rolls to determine which Province it is going to go to (in the second of the two rolls) the attract immigration adds some weight to that state's provinces to the roll.