1) Download L2Editor by lordofdest:
2) Open any retail package you want like LineageEffectsTextures.utx you mentioned (remember that custom servers might have their files encrypted with various software like smartcrypt, so if you can't open them it's normal because you have to decrypt first.)
3) After you open find the texture you wish to change and just upload your new texture by giving it same name, package and group with old one.
4) Save it and encrypt using mxencdec tool.
Package = the name of the package (in your case LineageEffectsTexture is the name)
Group = is just for organization and have no impact in game. However if you're editing a retail texture, be sure to use its group name when you import your new texture.
Name = is the name of your texture which is used by the item, html etc. you're editing.
Note: Take a look at some guides like this:
they will help you starting.