Can someone give me advice on how to use location cards as the GM? I am a little confused.

Thanks!

If there are multiple cards I put several on the table (for example you could have a boat location card and beside it a deep river location). Then the players just add their standups next to the card where they are and are allowed to read the text in most cases.

If there is only one location for the moment, I generally just reference the back of the card to see what special effects it has and describe the location for the players, for example they might be at the rowdy tavern location and then I just reference the rules about that place (allthough outside the rowdy tavern there might be a shadowy alley or some such).

Normally when I plan for an adventure I gather those locations I find useful for the adventure and then during the sessions I use them when they fit. Not every place need a location.

The thing I did wrong in the beginning was a lack of planning. I just thought I could whip out a location on the fly, That did not work at all (for me) and thus I hardly used them in the beginning. But now that I've started to prepare by reading them through and selecting the locations most appropriate for the adventure I'm going to run, I have a good grasp on what to use when and then it works wonderfully.

In my oppinion the Location cards are really good, since it adds some flavour to important (or less important) places.

Yup to all the above.

They can be abstract layouts of a town or village (Marketstrasse, Inn, Temple, Noble Mansion) or they can be simple indications of one location where an encounter takes place. For example in my last session I combined features of Bandit Camp and Cursed Ruins to be a warehouse where a cultist sect is meeting.