The pin of the press-in mandrel should have a slightly negative tolerance and have a shoulder! (Hiting in a plain bearing with a hammer is NOT effective and can lead to damage to the bearing! When pressing in, oil can be applied to the OD of the bearing. The bushing should always be well centered on the bore!
Carefully operate the press until the bearing centers over the installation stage and the bearing slides into the housing bore.
Once the bearing is fully pressed in, remove the mandrel. In the case of flanged plain bearings in particular, care should be taken not to apply more force than is necessary. This could lead to deformation of the collar, especially in the case of bronze bearings
Make sure the bearing is fully pressed in at the level of the housing bore. Especially if neighboring or adjacent components are to be mounted flat at this point!