ok,
WEP is wireless encryption, you will be asked to set a key - and you require the same key entered on whatever device you want to access it.
The best way is to get it working without encryption beforehand and add that after, do it one step at a time.
Dont worry about the channel - the preference on channel is only important if you have a high number of users of similar equipment in the same building.
Your modes, A, B,G,N are about the bandwidth that will be available. you will only be able to communicate on a compatible mode - so if you have a 802.11b card it should be able to do a/b but may only be able to be able to do 802.11b.
Whilst your modem may be able to do 802.11n if your wifi card is so old it can only do B then dont waste time by letting it negotiate through the spectrum.