[TYPO3] typo3 4.0 extension installation

[Rocky]

Hey Group,

Can any of you tell me how to import extensions from online repository 
in typo3 4.0 please? In version 3.8.1, I just need to put the ext key 
and hit "look up" and it will give me the extension as long as I set my 
setting in EM. But this is not the case in TYPO3 4.0. When I try to do 
the same thing, I got the following error:

##########
  Fatal error: Allowed memory size of 26214400 bytes exhausted (tried to 
allocate 408 bytes) in 
/home/lover/public_html/typo3_src-4.0/typo3/mod/tools/em/class.em_index.php 
on line 1424
###########

If any of you could give me some hint, I would really appreciate it?

Thanks a lot in advance!
Rocky